The England forward has been linked with a move away from City after finding himself on the bench on a number of occasions towards the end of the 2020-21 campaign.
"It is just happiness, just being happy, enjoying my football and that is what I am doing being here with the national team," Sterling said.
"If you're not playing, you're not happy. That's me, that's been me since I was a kid, if I'm playing football I am really happy, if I'm not I'm not happy."
Sterling scored the winner for England against Croatia in their opening Euro 2020 group match.
But the former Liverpool man could not fire again in the 0-0 draw with Scotland on Friday, with the team's performance drawing criticism from supporters.
Asked about the reaction, Sterling added: "I do feel there's a bit of an overreaction on the whole in terms of I don't know if it's… I just feel there's more of a panic on the outside than inside the building.
"The players who have been at a few tournaments, who have huge experience, try to help the other ones.
"I don't see anyone in the camp that feels any pressure or feels hard done by. As much as we can inside the building the best thing we can do is focus on the training field, focus on what's being doing inside."