Manchester United manager Sir Alex Ferguson admits he 'fears' the idea of retirement, but concedes he is at the penalty shoot-out stage of his career.
Ferguson had previously announced his intention to retire at the end of the 2001/02 season before performing a U-turn to continue his association with the Red Devils.
He has subsequently added a string of further honours to the Old Trafford trophy cabinet and has enjoyed over 22 years at the United helm.
Speculation persists as to when the 67-year-old will eventually decide to relinquish the reins of the Premier League leaders and he acknowledged he assesses the situation on an annual basis.
However, the Scot also revealed the three factors which will determine when is the right time to step down, despite outlining his concerns about retiring.
"When I reached 60, I asked myself the question," Ferguson told L'Equipe. "I almost left.
"But I quickly realised, with my family, that it was a mistake. Today, I fear the idea of retiring.
"I have been on the train for so long that when I get off I fear my system will collapse.
"I have decided not to ask myself the question any more.
"Three things can make me stop. 1. My health. 2. If I don't take pleasure any more. 3. If I don't have the strength for new challenges any more.
"Each summer, I have a look at those three things. I go to my doctor first. I had a pacemaker set up four or five years ago.
"Today, I am playing the penalty shoot-out of my managerial career. I know that. The rest is decided between me and me.
"I see my doctor every summer. He says 'boss, you are 67. You will have more and more back pains. Getting up in the morning sometimes won't be easy'.
"This is the penalty shoot-out."