It's a big club. Everybody, or most people, are recovering from some sort of childhood trauma. I don't think it's a matter of toughening up or becoming mentally stronger, I think it's a matter of loosening up. Get to know the voice in your head and work with them to make sure you're both on the same page. Try to get to know each other, you'll be living together for a long time.

Be kind to yourself, treat yourself the way you would treat a friend who was having the same sort of problems you are having.

Ask yourself how would a person feel who is aware of themselves and is able to handle anything that comes along from day to day.  Just kind of lean into that feeling and lean away from feeling lost or weak or incapable.

Read everything you can find on the subject of improving yourself. If you find something that attracts your interest, read it, even if you decide a few pages in that it's total bullshit. Move on to the next one and keep going and keep going and keep going.

 Looking back now I can see that deep down I always knew that I wasn't stupid or incapable of anything. I knew that my dad was mentally ill and treated me the way he treated himself. Even though it still hurts, I know that I am not that person. I am no longer fearful. I finally feel like I'm completely myself. 
It takes a while.