It's true that a person's attitude towards another, can be influenced by the other person's attitude sometimes. On the contrary, I wish to disagree with you on this ....

When I treated a cheating EX as if he was an angel, his heart judged him and he changed for good.

To me this kind of change makes no much difference, it's temporary. When someone cheats, it's a reflection of their vulnerability, something other people don't have control over for them. It takes a higher sense of understanding, self-discipline, strong resolve and commitment for one not to cheat.

A person may have an amazing and sound personality, yet might still become a victim of terrible attitude if he or she is still convenient and conversant with the environment of his/her vulnerabilities. Well done @ogoowinner, nice one