Is it possible to forget the past and really become a new person?

It's easier if you get "closure".

Pledge not to repeat any mistakes you may have made, and this frees you to dislike your old self but love your new self. Seek help in understanding the motivations of others in what happened.

Then use a technique called "Stop Thinking". Think "stop!" and distract yourself instead of dwelling on bad thoughts.

<3 <3 :)