Ferguson left his post at the end of last season as the most successful manager in British football history.
In his 27 years at the club, the Scot's haul of trophies included 13 Premier League titles, five FA Cups, four League Cups and two Champions League crowns.
Yet Ferguson, who remains a director and club ambassador at United, knew the time was right to stand aside.
"My reaction was that I knew it was the best thing for me. I knew I'd done my time," said the 71-year-old to the Daily Telegraph.
"My attitude was 'the only way I could really enjoy my life was to forget it', because you can become withdrawn about what you're going to do.
"'Am I going to miss this?' My attitude was 'I'm not going to miss it. My time has come'. I'd picked the right moment. The successes were mindboggling, to think what had happened to me in my career at United. Forget the past. It's no use to me."
Ferguson is revelling in life away from the spotlight although he is still keen to play a role at Old Trafford and has confirmed he is in regular contact with Moyes.
The former Everton boss has endured a chastening start to life as United boss after losing three of his first seven Premier League games in charge although the 50-year-old still has the backing of Ferguson, who would be prepared to offer his fellow Scot any help should it be required.
"My life as a United person continues," Ferguson added. "And that means winning; enjoying watching them winning. I don't need to worry about refereeing decisions, agents or the press any more.
"I'm a spectator with responsibility. I'm a director and I want to make a contribution as a director that will play a part. We've got a young chief executive now (Ed Woodward) who will need help, I think. And David Gill (his predecessor) is still there to help him.
"We've got a young manager and I'm there to help him. We've had a lot of dialogue, David (Moyes) and I, over the last few weeks, and he's been very, very good. He's been very open about what his plans have been. Any help he's needed or wanted, he's got it there."