Can a guy change completely?

A guy I know ( I am not his girlfriend) has decided to stop drinking for a while. His girlfriend requested that he stops seeing his friends, comes home right after work, and basically does what she says.
He used to cheat on her, drink excessively, and hang out with his friends all the time.
Can a person change so drastically that they basically become a new person? It has been two weeks but he is already mad that he had to stop drinking. He also told me that he is still texting with a girl he had sex with behind his girlfriend back.
How realistic is that he will be able to become who she wants him to become?
Will he be back to his old self soon? What do you guys think?
Updates:
+1 y
He also told me that the girl he had an affair with is crazy about him and he wants her so they text all the time. I don't think that is helping that they stay in touch
Can a guy change completely?
6
3
Add Opinion