If you have a few minutes, this post about 7 destructive thought habits that can hold you back from living a happier life has some really great points, especially number 7. That website has lots of other great self improvement posts as well.
Want some encouragement to tell off your negative inner voice? Click over here to read a post from one of my favorite bloggers, Lisa-Jo Baker. She's incredibly raw and honest in her writing that it can't help but move you in some way.