Peter Robinson has said it seems an appropriate time to step down as Northern Ireland's First Minister and leader of his Democratic Unionist Party, given his age and length of time in politics.
Speaking on RTÉ's Six One News, Mr Robinson said his family will be rejoicing at the fact that he will be spending more time looking after himself, following his health scare in May.
"People who aren't directly involved probably don't know the rigorous role that any minister of any type, but particularly a First Minister, will have.
"They don't know the rough trade that is politics, generally. They don't know the kind of pressures that are applied; the tensions that exist. All of that is there.
"I suppose you come out of hospital after that kind of event and with the wise words ringing in your ear from consultants and I kept it deciduously for at least two weeks and then, gradually, I've just slipped back into the bad old habits."
Mr Robinson, 66, said the Sinn Féin organisation is different to the political structures he is used to: "You have to understand the processes that are involved with those that you are working with." He described the Sinn Féin system as slower.
He said that he would have found a lot of people in Sinn Féin difficult to work with, but that Martin McGuinness has been "relatively easy to work with on a personal basis" and that their relationship had always kept a civilised manner.
Mr Robinson made the expected announcement in an article in the Belfast Telegraph, amid growing speculation he would outline his departure plans at the DUP's annual conference this weekend.
The move comes just days after Mr Robinson struck a deal with Sinn Féin and the Irish and British governments to save the faltering power-sharing administration in Belfast.
"I think it would be disrespectful to the party membership if I was to go through a conference with the pretence that I would be leading the party into the next election," he said.
"I think they have a right to know what the circumstances are."
Peter Robinson: From rabble rouser to steely strategist
DUP leadership - The Contenders
North Belfast MP Nigel Dodds will be among the favourites to take over as DUP leader.
However, with Mr Dodds based in Westminster, another senior party figure may take on the role of Stormont First Minister.
Current Finance Minister Arlene Foster has been touted as a potential leader of the power-sharing coalition.
Mr Robinson said he would remain in the post until the Fresh Start agreement is "bedded in" - a period he indicated could last into the early new year.
"There are a number of fairly immediate decisions that have to be taken and they [party officers] will then organise a transition," he said.
"In the meantime, I don't want people to be focusing on issues of succession yet. When the party officers declare the process - which I guess would be at the beginning of next year - then people can start looking at who the successors should be for leader and First Minister. Let's focus on the agreement and getting it bedded in."
Mr Robinson, who replaced Ian Paisley as First Minister and DUP leader in 2008, said he had wanted to secure a number of specific objectives before leaving.
These included stabilising the power-sharing government, the DUP retaking the East Belfast Westminster seat he lost in 2010 and setting a date for Northern Ireland to determine its own corporation tax rate.
With all those accomplished, he said the time was right to step aside.
"For anyone who is not very young to go beyond two terms is stretching it," he said.
"There are massive pressures on anybody in this job. You do need to renew political leadership, bringing in people with perhaps more energy and people with new ideas."
During a heated Stormont debate yesterday, on a motion to allow Westminster to legislate to introduce stalled welfare reforms in Northern Ireland, a number of political opponents suggested the vote was being rushed through to leave the stage clear for Mr Robinson to make a statement at his weekend party conference.
Tuesday's 'Fresh Start' agreement resolved the protracted wrangle over the non-implementation of the Government's welfare reforms, and a number of other disputes which had pushed the coalition Executive to the verge of collapse, including the fall-out from a murder linked to the Provisional IRA and an acute budgetary crisis.
However, the accord has been fiercely criticised by victims' campaigners for failing to secure consensus on new mechanisms to address the painful legacy of the Troubles.
Northern Ireland Deputy First Minister Martin McGuinness described Mr Robinson as an intelligent man who had the leadership abilities to bring the DUP into the Northern Ireland institutions, adding it was a difficult job being leader of the DUP.
Asked if Sinn Féin could now become the biggest party in the North and provide a First Minister, Mr McGuiness said his priority was the ongoing success of the peace process.
Sinn Féin President Gerry Adams was among the first to wish Mr Robinson well in retirement, taking to social media to pass on his regards.
Good luck 2 Peter Robinson.
— Gerry Adams (@GerryAdamsSF) November 19, 2015
Fianna Fáil leader Micheál Martin also wished Mr Robinson well saying he always found him to be a pragmatic and straightforward politician who was serious about moving Northern Ireland forward.
Analysis: Northern Editor Tommie Gorman
Abrasive, shy, clever, fiercely competitive, Robinson has been the DUP's master strategist for decades.
You could see that it was part of his strategy to try to leave against a successful backdrop, and I think that was part of the dynamic that got the deal over the line in recent times.
There is no doubt that he has been thinking about it for months, or even a year or two, and I think what maybe finally decided it was that after that illness earlier in the year he had that burst of adrenalin, that relief that he was still alive and that he had come through his illness.
You want to leave before you're pushed, you want to leave when things are going well and you have something meaningful to hand over.
If you look at the deal that was achieved just two days ago it was about as good as it gets.
In some respects, you could now see the DUP carving up the leadership responsibilities, but my money is on balance that Arlene Foster might have the two roles.
