Sir Alex Ferguson revealed he made his decision to retire as manager of Manchester United in December.
Ferguson was given an emotional farewell Sunday in his last game at Old Trafford, which United won 2-1 against Swansea, before the English Premier League champions were presented with the trophy - the 13th and final one during Ferguson's reign.
The legendary Scot admitted the decision to call an end to a near 27-year reign at Old Trafford had been made at Christmas.
"I decided at Christmas," he said.
"Cathy's (Ferguson's wife) sister died. She had lost her best friend and she has been isolated.
"For 47 years she has been the leader of the family. She has made a lot of sacrifices for me."
Ferguson admitted he nearly spilled the beans about his retirement on a couple of occasions earlier on, but made the decision to make it public following the revelations on his future last Tuesday in several British papers.
"It was difficult to keep it a secret," he said.
"Sometimes we nearly blurted it out to the family and we told our sons in March but my brother didn't know until Tuesday.
"I wanted to tell the players first and also my staff. Unfortunately there were rumors going around on Tuesday so we started to speed it up a bit."
In a game which was played in a party atmosphere, United typically took all three points courtesy a late goal from Rio Ferdinand.
Javier Hernandez, in for Wayne Rooney, who did not even make the squad after asking for a transfer, opened the scoring for United, before Michu levelled the scores early in the second half.
The game looked like it was heading for a draw, but as has been witnessed so many times in the Ferguson era, United struck late, this time through Ferdinand.
"It was an honor for me to be here today," Swansea manager Michael Laudrup said. "We have witnessed something special in football, not just in England but across the world.
"I can't remember Manchester United having another manager and it is a credit to him that he has managed to build teams not just for the present, but for the future as well."
