Grealish left City last month to join Everton on a season-long loan.
He told Sky Sports: "Of course, people have a perception of me, but there's nothing I love more than playing football. Whether it's on the training ground - I just love playing football.
"People say, 'He likes to go out, he likes to party' and I do.
"I would also like to live my life and enjoy it, but there is a time and place for it.
"If I'm to be honest, then I probably haven't always chosen the right times - sometimes at City, for example, I didn't do myself any favours, I admit it openly - but I don't mean that it was all due to that,."
Grealish also said: "People ask me, 'What happened at City?' But I had two good years there. The first year was about getting used to it all: getting to the club for that sum of money, the pressure and understanding how the manager would play and adapt to the environment.
"Second year we won The Treble and it was an incredible year. I loved it. The third year - I have to take that on my own way. I feel I didn't do the right things that season."