Catholic Bishop of Clogher Liam McDaid stood down at the weekend after revealing he was suffering from Parkinson's disease.
Dr McDaid said the condition had become "increasingly problematic" and was beginning to "interfere" with his work.
In a heartfelt letter read out at Masses in the diocese yesterday, Dr McDaid, from Bundoran in Co Donegal, said Pope Francis had accepted his resignation in light of medical advice.
He revealed that his health problems first emerged seven years ago when parishioners "noticed the tell-tale tremor" in his hands at the altar, which was subsequently diagnosed as Parkinson's.
"When I was appointed to take on the responsibility of being your bishop, I was advised medically not to let this condition prevent me from taking on the challenge but to keep it under review and follow medical advice," said Dr McDaid.
"I was fortunate to have excellent medical care but it is a neuro-degenerative condition which over time gets worse rather than better, to put it simply."
Describing his schedule as "stressful and demanding", he said it was "inevitable" that his condition would become "increasingly problematic" and "interfere with my capacity to fulfil my responsibilities".
The 71 year-old explained how six months ago his medical team "called time" on his role as bishop and quoted part of a report by Professor Daniel Healy, his consultant neurologist, who wrote: "I have advised him on medical grounds that he should retire from his position as Bishop of Clogher.
"Bishop McDaid has bravely tried to continue to the best of his abilities with his mission and episcopal responsibility. However, I am now of the view that this is having a negative impact on his quality of life and health."
"That does not leave much room for discussion, especially when your body appears to be giving the same message," said Dr McDaid, adding that the diocese "will not be left rudderless" in his absence.
Reflecting on the future of the Church and where he believes the problems are, Dr McDaid said some parishioners "find it difficult to see beyond the bishop and priest".
"When adults and parents opt out of church on account of the shortcomings and failures of the messengers, is this not impoverishing themselves and their children, effectively depriving them of the nourishment and guidance which they can find only in the message of Christ?
"I am not saying these things out of pique or in a rant, but out of concern for my Church and its members. We are missing out on the talents and energy of so many good people," he commented. Dr McDaid, who held the position since 2010, said it was "sad to see" people "wasting so much precious time criticising and denigrating the Church when they could do so much for their community".
And he claimed that communities now "suffer a similar loss in our schools".
"Teachers do some marvellous catechetical work but they feel they are often working in a vacuum with little or no support in comparable instruction from parents, and little or no church attendance to give it all a community foundation and backing. If we had these members back and involved, what new life and vitality could we then give to each other's flagging spirits?
"Throughout the diocese I have witnessed and experienced much joy and neighbourliness among people as together they seek to build up the community. This is despite the obstacles, current and historic, that often lurk in the background," he said.
Dr McDaid added that "much progress" has been made in "overcoming obstacles of the past and present" throughout the wider Church, and paid tribute to Archbishop Michael Jackson of Dublin and of his successor as Bishop of Clogher, Bishop John McDowell.
"Together with others, they have moved ecumenical respect and activity to a new level."
In concluding his letter, Dr McDaid said it had been a "privilege" to serve as bishop and added: "It is with some reluctance that I go, yet I know that it is the right decision.
"I offer my apologies and ask forgiveness from anyone I have wronged or failed in my ministry. It is time to prepare for the next phase of the journey. I ask you to remember me in your prayers, as I will continue to remember all of you."
Never one to hold back, Dr McDaid regularly shared his thoughts on society and Church, including likening the child sex abuse scandal that rocked the Catholic Church to a "surgeon's knife" that "has been painful but necessary".
During his first speech as bishop six years ago, Dr McDaid said: "Society has forced us in the Irish Church to look into the mirror and what we saw were weakness and failure, victims and abuse.
"The surgeon's knife has been painful but necessary. A lot of evil and poison has been excised. There comes a time when the surgeon's knife has done what it can, is put away and a regime of rehabilitation for the patient is put in place. We have been brought to our knees, but maybe that is no bad thing."