The young Italian has become a crowd favourite at Manchester City and, as he proved during Sunday's encounter with Arsenal, is capable of making a match-winning contribution for the club.
However, there have also been far too many off-the-field scrapes which Mancini feels are holding the youngster back.
"Mario can improve every week and every month," he said.
"He is young and when you are a young player, you improve always.
"I hope the New Year can bring a different way for him and that he can understand if he wants to play well and have a good private life, he should have good behaviour always, not for one week yes and then change for two days.
"Every top player has a good private life and a good behaviour.
"They are the first in training every day. This is the way it needs to be for him."