The 36-year-old started every game of City's peseason tour of Asia and will likely be in goals against Liverpool in the Community Shield on Sunday.
"I was calm from day one," he said. "I knew I would overcome the situation and nowadays, I'm feeling pretty happy about where I am, having left the injury behind – and a tough one at that.
"I was calmed because I know what these injuries mean. I was also well-informed about it – I read a lot about the injury and all you need is time and dedication.
"You have to work on it for a lot of time as well to avoid any relapse, and not worry about it after the recovery.
"I think both the physical and mental side are equally important. If you don't have the right mindset, it's going to be more difficult to overcome the situation and I think the body is just as important. In my case, my mindset was key.
"I had to go back to normality without any sign of tiredness or hassle in the area I had hurt. When you get there, it feels very positive.
"I feel good. The recovery was very good and within the expected times."