The Serbia international was linked with a move to Italy after failing to hold down a regular place during the 2012-13 campaign.
But Kolarov felt he still had something to prove at the Etihad Stadium and, after the apointment of manager Manuel Pellegrini, vowed to stay on.
The 28-year-old now feels his decision to resist interest from elsewhere has been justified.
Kolarov told City TV: "Last season I was thinking, because I didn't play a lot, it was maybe a good thing for me to move.
"I had a couple of opportunities but I refused everything because I didn't want to go from here, (having not) shown the people what I can do.
"Now this season I have had this opportunity and shown what I can do.
"For me it is like a victory, personally, for myself.
"If you play regularly you can improve a lot every game."
Kolarov, who has started 28 games and scored four goals this season, must still battle with Gael Clichy for a place at left-back.
But despite that competition, Kolarov feels his game has been allowed to flourish under Pellegrini.
Asked what Pellegrini had done differently for him, Kolarov said: "Nothing special, (he) just gave me the opportunity to play more regularly.
"So I think his way of thinking is maybe the good thing (for) how I am playing football.
"We are playing a lot with wings, attackers. It is good for me.
"He gave me the opportunity to play more regularly, so I am just showing what I can do.
"I think I am having a good season so I hope I can finish in this way."