Paul McKenna has made millions out of his guidance on how to make us happy, confident, thinner, richer and now smarter.
Yet the 'hypnotist to the stars', whose wide circle of friends and clients includes Simon Cowell, the Beckhams and David Walliams, was unable to assuage his own intense grief when his father died after a long illness last year.
"His death made me question my own life, and realise how precious and short life is," says McKenna (48) whose books (including I Can Make You Happy/ Sleep/Thin/Rich) have sold more than any other non-fiction author in the UK.
"Everyone tries to control their feelings by some external means. If I felt really sad I'd probably drink more, but the next day the sadness is still there.
"Some people bury themselves in work, but ultimately, if you ignore your feelings they'll just shout louder.
"It brought it home to me. Major life incidents like this get you to question your values.
"And while the foundations of my values haven't changed at all, that doesn't mean I don't take time to check out who I am and where I'm going."
After his father died, he didn't do much for a few months. He left his luxurious home in the Hollywood Hills, where he has lived for five years, to spend time in England with his mother, whose health had also been ailing.
It was important to give himself some time off to go through the grieving process, he reflects.
"I still have moments when I really miss my dad but I don't want to be dysfunctional or sitting crying all the time. That's not what he would have wanted."
His latest book, I Can Make You Smarter, took longer to finish because he needed to spend time with his family, he reveals, and the death of his father gave him a different perspective on life.
"I thought to myself, if I died tomorrow, I could look back and think, 'I've led a good life'. But then I thought, 'Hang on a minute, I could up my game and do even more'."
Even more? But how? His self-help books have grossed more than £17m in the UK alone.
He has a huge celebrity clientele, lives in a luxurious house in Hollywood, drives Ferraris and only last year turned down the chance of buying Michael Jackson's £19m Los Angeles mansion.
Yet his drive to do more never abates and it's not about money, he insists, but a desire to help people.
I Can Make You Smarter is perhaps a throwback to his unremarkable childhood in Enfield, Middlesex. The son of a builder and home economics teacher, he didn't excel in education.
"Many people are told at school, 'You're not good enough, you're not smart', and assume those things are true. But you don't have to buy that," he says.
"I was told I would never amount to anything. What I didn't realise was that learning by rote, which is how we were taught, is perhaps the stupidest way to learn anything, and actually we're all very good at learning.
"Research shows that while school has many positive qualities, it does tend to stifle divergent and creative thinking out of a necessity for conformity."
For much of his life he felt he had something to prove.
"I've got a cantankerous nature. If somebody says, 'You can't...' I say, 'Well, why not? Maybe I can...' Part of my personality has sparked this."
On leaving school, he began DJing in Topshop at Oxford Circus and went on to work for Capital Radio, where he interviewed a hypnotist who fuelled his interest in the field.
The rest is history.
Today his marketing skills seem almost as acute as his self-help talents.
"I don't have all the answers. I'm not a guru, more like a technician. I have good systems to help people in certain areas, like weight loss. I think of myself as a solution business.
"My job is to take the airy-fairy, intellectual ramblings out and make it very commonsense and easy for people to get the solutions they want."
He's hoping to develop phone apps and other digital media for his techniques: "YouTube is now the biggest TV channel in the world. You can get a bigger audience on there than you can on some terrestrial TV channels, if you make the right kind of programme."
He has several TV projects on the boil in the US and is working on a hypnotic gastric band technique, where you hypnotise someone to believe they have a gastric band and as a result, they eat significantly less.
"I think to myself, 'What do people need?' and look at what people want in life, where there is a gap. Smarter is not just about being more intellectual. Right now the world is in a massive process of change and we need to adapt. A lot of this book is about adaptation."
Yet McKenna himself has been unable to adapt to a life shared with someone else.
While he has had many girlfriends - and even lives platonically with an ex-girlfriend, model Clare Staples, who is his manager - he's never married.
"I had a relationship for most of last year, but once again I'm single," he reveals. "It's probably my fault, I'm willing to admit that. I've said half-jokingly in the past that I'm commitment-phobic but maybe I'm quite happily so."
He's started horse riding with Staples and, while switching off doesn't come naturally, he says he's enjoying many of the things that are a part of Californian life and meditates regularly.
"My life has chilled out a little bit now. These past few months have been so frantic and I've got so much done, but I don't think I could live happily at that level.
"What I have to do is prioritise, find out what's really important to me and produce the maximum result without burning out. I'm enjoying life far more in many respects than I have done for a while."