There are podcasts called Codependency No More (if I recall right). They interview some BRILLIANT people (counselors, seasoned Alanon veterans, doctors, psychologists etc) , and wiping out negative self talk is a huge focus in several of them. I really recommend these. Also the book - Conquering Codependency and Shame tackles the subject a lot. Both helped me so much....
I did't even realize the level of negativity I had towards myself, and the insanely high expectations I had of myself until I started reading that book. Like....if anything I thought I was self absorbed and egotistical and selfish. Negative self worth, poor self esteem, and lack of value of myself are never things I thought I had going on - even remotely - until that book and those podcasts.
Once we recognize that voice, it gets easier and easier to argue it, then squash it!