Fletcher fought to recover from ulcerative colitis, an extreme condition affecting the colon, for several years before making his latest comeback in United's 3-0 win at Aston Villa on Sunday.
The Scotland international had already taken two breaks from the game in the hope of finding a way of managing the condition without success.
And as he prepared for a third operation he was more concerned with how he would cope with the rest of his life rather than his struggle to return to action at Old Trafford.
"I couldn't leave the house," he said.
"Simple stuff, like taking my kids to the park, going for a meal with my wife. The nature of the illness meant I just couldn't do it. There was the exhaustion side as well.
"I always believed one of the medications would work. Unfortunately that wasn't the case.
"Ultimately that was the reason I went for the operation."
Although Fletcher's surgeon was confident surgery would prove successful, the consequences of failure were laid bare.
For a 29-year-old, supposedly in the prime of a career that had already brought him four Premier League titles, an FA Cup and a couple of League Cups, it was a bleak prospect.
"There was a day in May when we said 'this is it'. Once I came out of that operation I would know whether it had worked or not," he said.
"There were no guarantees. If the operation was not a success there was no way I would be able to play football and my everyday life would have been very difficult.
"It was very emotional. There was a lot of fear and anxiety. I put all my trust in the surgeon.
"I didn't want to give it up. I worked hard to be a professional footballer. I always have. I always kept that determination.
"I was doing this operation, not just to have a quality of life but also to get back playing football."
Fletcher achieved his aim at Villa Park on Sunday, being introduced as a second-half substitute as David Moyes' team cruised to victory in the Premier League fixture.
"I am back to normal. I do not have ulcerative colitis. I am back playing football in the Premier League," he said.
"I don't want to take it easy. I've done enough of that. I am just like anyone else."