The Scotland international has struggled with ulcerative colitis since December 2011 and made his first appearance since Boxing Day of 2012 as a substitute in his side's 3-0 win over Aston Villa.
Fletcher revealed that he had been unable to leave his house for long periods and faced surgery which could have ended his hopes of resuming his career.
"I couldn't leave the house, it was as simple as that," he told reporters. "I couldn't take my kids to the park for a kickabout. Simple stuff. I couldn't go for a meal with my wife, just because of the nature of the illness.
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Following surgery, Fletcher faced a nervous wait for doctors to confirm whether or not the procedure had been successful enough for him to resume his career.
"There were no guarantees with the operation," the Scot recalled. "If it was not a success there was no way I would be able to play football.
"I didn't want to give it up. I worked hard to be a professional footballer; I always have. I didn't want to give it up. 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.
"Once I came out of that operation it was going to be 'this has either worked or it hasn't'. It was a very emotional day.
"There was a lot of fear and anxiety. Thankfully I was in the hands of an unbelievable surgeon. I put all my trust in him. He was confident, as long as I did everything right.
"All the tests were right and, when that moment came, it was such a relief.
"I am back to normal. I'm standing here now [and] I do not have ulcerative colitis. I have come through that now. I am leading a normal life. I am back playing football in the Premier League."