Hart makes his Irons debut today at Manchester United.
On City struggling to find the right goalkeeper since he left, Hart told the Daily Mail: "That's their problem. I need to look after myself, I need to be selfish in this situation.
"My feelings for Manchester City will never change, I'm eternally grateful to them as a football club.
"They took me as a 19-year-old boy from Shrewsbury Town, took something of a punt on me, and I've had some fantastic times there and built some really great relationships.
"The fans have been so supportive of me, even in the last year. As far as the business side of it goes, new managers and new opinions, that's football, I just have to take it on the chin."