It's that mindset that you have that needs changing. Only you can change it. The way to do that is to give yourself the positive affirmations that you lacked when growing up. In many ways, we need to reparent ourselves.

If you see yourself as your own child, it's easier to think positive things about yourself. When the old tapes of self-loathing start playing, tell them to hush and tell yourself, "I am a good person. I am a worthy person." Whatever the argument going on in your head that is negative, counter it with the opposite. If you think "I am lousy at...." Say "I am working at being good at..." If you can't do that, just tell the old tapes to "Shut up! I'm not listening to you!" Like anything else, it takes time and practice, but it's sure worth a try.