I was very hard on myself.
Why were you so hard on yourself?
I didn't like my personality and I wanted to make some changes
Even if you do not like yourself, you should be kind to yourself. You deserve the love you need, so be kind to yourself.
Nah, I'm going to hurt myself.
I understand that there are aspects of your personality that you may not like, but hurting yourself won't change them. Cut yourself some slack and gently work on the changes you want to make without being harsh.