For Bobby Mathieson, being part of a UVF gang that murdered a Catholic man eventually left him wanting to kill himself.
Ten years into his life sentence in the Maze, the back-slapping camaraderie with fellow paramilitaries had worn thin.
Studying maths and art A-levels was a fulfilling distraction, but when he closed the books and put away his canvas, he would paint a mental picture of his own life - and the sum total was worthless.
Playing football allowed him to show off the silky skills that had seen him signed as a teenager by Linfield and, outwardly, his sporting prowess added to his status as one of the big personalities of the H-blocks, full of character and banter. But inside, in his own head, he felt small, despairing and empty - and increasingly that vacuum was filled with a deep self-loathing.
Ironically, as he tells it now, fracturing his leg on the pitch proved a lucky break, though it didn't feel like that at the time. Literally stopped in his tracks, Mathieson (59) had time to think and found himself consumed with guilt.
"Along with the bigger stuff I'd done, everything I'd done in my life was being laid out in front of me, right back to when I was no age," he says.
"I remembered stealing biscuits in a shop and it just went on from there. It started driving me mad.
"Everyone has hidden sin, stuff they're ashamed of and don't want to share but want to get out of their life.
"I didn't like the person I'd become and I believed every single person could see the person I'd become. My mind became paranoid, telling me that everybody in the prison was going to kill me, that they were all in on the plan."
Mathieson was moved from the Maze to the psychiatric wing of the hospital at Maghaberry prison.
"I was medicated for the next four years. I still felt low and rotten but talking to psychiatrists helped," he recalls.
We are 45 minutes into our interview when we reach this juncture about the first of two breakdowns that prove pivotal in his journey from prison to pulpit, where he regularly gives his testimony.
Mathieson talks quietly and quickly, and the story that unfurls is extraordinary in its happenstance; it's a morality tale of the Troubles, with script twists so incredible that they wouldn't make it onto the screen.
He was the football-mad youngster from a good home who spent two years in hospital wearing calipers; when they were taken off, he practised so hard he was signed by an Irish League side. Yet the sport he loved put him on the road he bitterly regrets ever turning down.
He was the young joiner who joined the UVF and after prison quickly fell back on his trade and "was soon making loads of money, big house, lovely cars, flying off on holiday three times a year, drinking with millionaires".
He was the little boy who sang Jesus Loves Me in Ballygomartin Road Baptist Sunday School and even in the most abject circumstances behind bars, whenever he heard Rev David McIlveen or another preacher talk about sin, forgiveness and eternity something - the cadences? the message? - would settle upon him and he longed to get back to who he had been when he was singing those choruses all those years ago.
Mathieson walked free from prison at the age of 34. Loyalists organised a welcome home event in east Belfast.
He attended it but "wasn't really there at all. These lads want to celebrate you, bring you back into the fold. But I was a different person. I was me now. I was done".
He met his wife Alison, who had two young children. They married and had another three children. Mathieson went self-employed, worked from 7am until 10pm, made good money and the family enjoyed the spoils.
But no matter how quickly he turned his life around, his past kept flashing up in the rear view mirror. Twelve years after his release, he again felt suicidal.
Mathieson, who frequently reaches for Scripture to illustrate a point, admits: "It says in the Bible what shall it profit a man if he gains the whole world but loses his soul. That's where I was. I knew there was a God because He had convicted me of all the suffering I had caused.
"When I was inside, I thought He'd passed me aside because He didn't want someone like me. I was trying to live, but I couldn't live with what I'd done.
"My mind started going; I thought my mum hated me, my wife hated me, my kids hated me. My mind told me I was evil, that my evil would infect my children, that I'd end up dragging them into Hell with me, that I'd be better taking my own life."
Panic-stricken, his wife rang the pastor who'd married them. He prayed with Mathieson and told him that if he tried to kill himself, he risked alienating his family.
After another wretched two days, Mathieson "fell on my knees, I was repenting, from the top of my head down through my body, I felt this pour out through me. I believe that's the day I got saved, the day God set me free. I went to my front door and physically kicked the Devil out through it.
"Jesus came to save sinners like me. I could be beaten to death for what I'd done, but Jesus was beaten to death and crucified for me. That has set me free from guilt. I now stand in Christ."
He talks for some time about Biblical figures who committed murder: Moses, who killed a man; David, who committed adultery and arranged for his lover's husband to be killed; the disciple Paul who persecuted Christians but turned his life around. "I was told even though you have done horrendous things, God can forgive you. I had to check the Bible, and it's true."
Mathieson got involved in terrorism despite his working class Protestant family's best efforts. Until he was 10 he'd lived on the Highfield estate, where he'd played with kids from neighbouring Ballymurphy. When the Troubles erupted in 1969 his mum, a home help, and dad, a fitter, uprooted the family to the quieter environs of Dundonald.
As a teenager, Mathieson dabbled with flute bands and bonfire building - "it was just about celebration, like enjoying the Twelfth parade" - but it was football that brought him into contact with the UVF.
Fed up at repeatedly losing his place in Linfield's reserve team, a move to Glentoran was on the cards. Linfield wouldn't release him from his contract so he started to play for a small team in east Belfast.
"These lads were brilliant and I loved it. If there was a fight, well, I was also a boxer so joined in. We all had each other's backs. But they were all paramilitaries."
It was 1980, the hunger strikes had begun and unionist politicians warned of the risk of a united Ireland.
"I joined the east Belfast UVF when I was 18. I went to the Third Force rally that Big Paisley took in Newtownards, but I'm not blaming Mr Paisley. I take full responsibility for what I did. Still, young people were being egged on and it wasn't lies either - the IRA were killing people, they were blowing things up. It was easy for someone like me to volunteer. People ask now 'what were you thinking?' I wasn't really thinking at all. If I had been, I wouldn't have joined anything."
Mathieson segues straight from this to details of the murder he was involved in. "I was arrested when I was 20. It was murder. I didn't actually shoot the person dead, but I was there. I was supposed to drop guns down to some people but then one of the persons wouldn't go [to do it] so I said I'd go. I pointed the gun towards somebody and the gun didn't go off. He was shot dead by the other gunman."
Who was Somebody? "John Gerald O'Neill," replies Mathieson, who says he was singled out to be killed by UVF hierarchy. "None of this was right. He was working in a garage."
There is a pause, then Mathieson, continues: "I was on a journey; I was on the road to no town. It wasn't because I hated Catholics because some of my family were Catholics."
What about restitution? Has he contacted Mr O'Neill's family? "No, no… but I would be prepared to meet my victim's family. It wouldn't be top of my list but if it's what they want…"
Northern Ireland is a small place and Mathieson reveals he had a brush with just such an encounter a few years back. His mother had given a book of his poetry to a neighbour. A workman in the house spotted it, asked the neighbour if they knew Bobby Mathieson and said he'd killed the brother of a close relative. When this exchange was relayed to Mathieson, he "went up to this guy's house and said 'if you meet him again, and he wants to meet me, I'm up for doing that'.
"What I'm saying here is 'Lord, I'm walking up to the door, if you open it, I will walk through'. I'm not making excuses, but you have to be careful how it's done. Friends have done this and it's been a disaster. They've been called liars, they were wrecked and other people were wrecked. I believe it will come when God wants it to come and if God is in it, it will benefit other people. It's a delicate operation but I'm not walking away from the responsibility of it."
Mathieson starts to weep before resuming: "I'd meet them 100% but it has to be them that wants it. How could I help them? How do I make good that? All I can say is sorry. I'll be held to account for it by God but thankfully I have Jesus's part in that too. I'm not hiding anywhere. I'm walking in the middle of everything.
"Some people stay the same, say it was a war and justify it like that. But loads of people can't live with what they've done, they don't know what to do with it. Some deal with it by drink, some with drugs, some with God, some check out."
Today Mathieson, who attends Bangor Elim church, fits floors where sometimes he "leads people to salvation in their homes". He also works in young offenders' centres and prisons, where he holds art classes, is on the chaplains' team and tries to turn lives around.
He was recommended to me as someone whose faith is genuinely held and he regularly speaks about it at church events. But he frets about talking to a newspaper because of the impact on his family and victims, and says he prayed for an hour before our interview. "You just can't throw your story out there and wreck people."
Mathieson draws solace from his art, which runs from fantasy images and a striking lion face to portraits. Often they have a message, either Scriptural or about how tribal loyalties in Northern Ireland are an accident of birth - or both. One shows George Best "who was led to the Lord in hospital by a nurse before he died walking towards the Cross" with republican and loyalist murals either side of him.
Sitting beside one that bears the inscription 'Every saint has a past and every sinner has a future', Mathieson talks about technique: "I start with the lightest colour and then get darker and darker. When you bring the dark in, you change the focus."