Carwyn Jones has said he wants to be remembered as being a "fair and honest" first minister after almost a decade at the helm of Welsh politics.
Mr Jones, 51, will step down as first minister and Welsh Labour leader in the autumn.
He made the shock move last Saturday saying he had been though the "darkest times" since Carl Sargeant's death.
A week on Mr Jones said he had decided to quit last September months before he sacked Mr Sargeant.
Former Communities Secretary Mr Sargeant was found dead in November, he is thought to have taken his own life days after being dismissed from the cabinet amid allegations about his conduct towards women.
Mr Jones, first minister and Welsh Labour leader since 2009, had been under intense pressure, with some calling on him to resign, since the Alyn and Deeside AM's death.
But in his first major interview since his news at the Welsh Labour conference in Llandudno, Mr Jones said he made the decision to stand down months before the reshuffle, which was always going to be his last.
He told BBC Wales's Sunday Politics programme few had known about his decision until the speech. He told UK Labour leader Jeremy Corbyn of his intentions before Christmas, but only told him the timeframe hours beforehand.
"I'll be honest, I originally thought ten years would be a nice period of time, but when I came back from the summer, all of a sudden the two years beyond felt like a long period of time – when you start thinking that way, it's time to make preparations to move on," he said.
"The reshuffle was designed to bring into government all those people who I thought would be future candidates."
Mr Jones plans to step down in December and then will stay on as AM for Bridgend, rejoining the back benches for the first time since 2000 after about 18 years as a minister.
He said his record as first minister would be "for others to judge" and there was nothing that was "unfinished".
His proudest achievements were saving jobs at Port Talbot steelworks and attracting Aston Martin to St Athan, but he insisted he had no regrets about decisions he made during his time in the top job.
Mr Jones, who said he had would not return to his previous job as a barrister, said he wanted his legacy to be "I was fair and I was honest".
"I have never shied away from difficult decisions or tried to conceal them in any way, never, and I think that's as much as you can ask to be remembered for as a politician," he said.
Carl Sargeant's death led to Mr Jones announcing several inquiries. Two have been completed, but an independent probe into the circumstances around his sacking is yet to begin.
The first minister's announcement to step down came shortly after an inquiry into claims he misled the assembly over what he said he knew about bullying in the Welsh Government in 2014, found he had told the truth.
The inquiry, by independent lawyer James Hamilton, was sparked following claims there had been a "toxic culture" of bullying within a previous administration.
Mr Jones said: "I don't think there is any government in history where every government at every time has felt entirely happy, that's just the way it is.
"I was a minister once, you do think sometimes, hang on a minute I can't talk to the first minister or I can't do this, it happens, that's the way politics is."
A leadership contest has been sparked, but so far, despite speculation about a number of candidates, only Finance Secretary Mark Drakeford has declared.
The outgoing first minister, who said he would focus on his promise to make Wales the safest place in the UK for women in his remaining time, said he would not allow any contest to disrupt the government or Labour group.
But he refused to speculate on what he will do next, if he will stand at the next election in 2021 or accept a seat in the House of Lords.
"My immediate priority is the next eight months, the last thing people want is to have a first minister who is thinking beyond December," he said.
Analysis by BBC Wales political correspondent Arwyn Jones
When we met at his home for the interview, Carwyn Jones was more relaxed than I've seen him for a long time; it's rare to see a first minister in his slippers.
He said last week's announcement was a weight off his shoulders after keeping the secret for over six months.
I wondered whether the events of the last few months made him think of standing down sooner, but Mr Jones insisted if anything it made him want to stay on longer to make sure he could clear his name.
However, he made a promise to his family and was unwilling to break it.
His supporters and opponents will trade statistics about how successful he's been, he thinks he had bad timing in taking over at a time when the public spending taps of the UK Labour government were turned off.
Whereas his predecessor, Rhodri Morgan, had large cash increases to the budget every year, David Cameron's austerity policies meant he has had to manage with far less in the coffers.
I found it surprising to hear him say he didn't have any regrets about his time in office. Of course, he could hardly reel off a list of failures, but surely there must have been something which was nagging away at him? Apparently not.
It was also striking for me to hear him say he only had three weekends last year where he didn't attend an event related to his work.
So what does the future hold? Well for one thing there'll be more time for his interests; fishing and taking his six month old cockapoo puppy for walks.
But before that Mr Jones said he felt energised now that there's an end point to his premiership.
With the promises he has made, there's a lot to fit into so little time, but if he succeeds, it might make for a decent legacy.