Dear Meander:

I believe that there is no way to change a core belief such as the one you described without upheaval, no short cut, no way around it. What can be done is make such a change slowly, gradually. Every time you feel that upheaval, you can take a break, and let the dust settle, so to speak.

There is nothing you can do to convince yourself that you are a good person, once this core belief is in place (that you are not a good person) except to go back to the time that belief was formed and see the reality of those circumstances, see and believe, with time and work. You may need the help of a quality psychotherapist to do this, little at a time.

anita