CBT basically aims to rid self defeating thoughts and attitudes. It's quite fundamental to good mental health.
Here's a basic primer on CBT
http://www.spiritsite.com/writing/davbur/part1.shtml
Especially check out the charts he has on which kind of thoughts causes which kinds of emotions and the effects of them. It lays it out really clearly.
Keep in mind that certain brain chemistries make it easy for you to fall into those self defeating thoughts too. To maintain a healthy brain chemistry, a diet rich in protein is crucial, as amino acids make up the precursors for our neurotransmitters. Good sleep and exercise are also very helpful.
If you need step by step help to change your self defeating thoughts, Burn's book is filled with activities that can help you with that.