I like to do what Louise Hay calls "mirror work" where I say affirmations and encouragement to myself in the mirror. It sounds hokey, but it really helps when I feel stressed and I need reassurance. I'm sure it would help with positive self-talk, too. Check out Louise Hay for some good affirmations. She's a new age guru, but you don't have to ascribe to all the new age stuff to benefit from her teachings.