Cole, 27, did not kick a ball for previous Blues manager Guus Hiddink yet refused to become disheartened - despite undergoing a second operation this summer after a setback on the road to recovery.
He said: "I've really missed my football and it has been hard to watch the team.
"But I'm 27 now and have been through everything in my career, so mentally I was able to stay strong and deal with it by keeping busy.
"Two years ago I missed the whole season with two different injuries but this has been the longest absence of my career in one whack.
"But it never drove me mad as I realised just how lucky I am to be a footballer, even an injured one. I came in to training every day and tried to keep a smile on my face."
Cole insists he is coming back stronger than ever as the Blues welcome QPR this evening, after rushing back too soon in a bid to impress former boss Phil Scolari.
He admitted: "I didn't play a single game last season when I was completely fit.
"I came back too quickly from an ankle injury through my desire to impress the new manager. This time I have taken it steady, had my MOT and now I'm back there."