Who says thinking means you're unhappy?

I can get over the fact that its alright that some people already have bad/ruined impressions of me. If they hated who I WAS, it shouldn't matter to the CURRENT me because it isn't who I AM anymore. Its just too bad I acted the way I did to make them want to drift apart.

Accept that, accept the failures, or we'll never move on.

Contradictorily,
I got upset when I realised I didn't know who I was anymore.
Without the 'who I was', there wouldn't be a 'who I am/will be'.
Without the past, there wouldn't be a future.

People said I've changed.
I don't want to lose everything I ever was, I just want to lose the bad parts. So where did all the good parts go to?

Is the only option choosing who I want to be?