A podcast I listen to, The Biggest Problem in the Universe, brought in Self-Defeating Thoughts as a problem. Thought you guys might be interested in it. Starts at 43 minutes but two quotes really stuck out to me:

"If I was hotter, skinnier, smarter, more interesting I'd have someone. Insecurity is one of the most useless emotions. I mean think about it, what has it ever done for you lately. What has insecurity ever done for you? Not a damn thing, right? And the worse part is, because confidence is the single most attractive quality a person can have, focusing on your weakness actually makes you less attractive."

"Embodiment of confidence changes the way you think, helps you achieve, you overcome everything. You overcome all your obstacles because you think there's always someone more attractive than you, someone more successful than you, has more money than you, more popular than you, it doesn't fucking matter. And it has everything to do with your inner thoughts, your inner monologue, what you actually think about yourself and whether or not you can achieve. Because you can put those thoughts into action. It changes the way you carry yourself."

http://thebiggestproblemintheuniverse.com/episode-67/