Mistakes Were Made (But Not by Me): Why We Justify Foolish Beliefs, Bad Decisions and Hurtful Acts

The core of the book centres around the idea of cognitive dissonance, where the brain has to reconcile two contrasting viewpoints. For example the self belief that "I am rational and intelligent" with the action "I am slowly killing myself by smoking". The dissonance could be resolved by concluding that actually I am neither rational nor especially intelligent, but of course no one wants to conclude that! So instead I look for levers to reduce the gap in the other direction. Smoking helps me to relax, and stress is a big killer, smoking helps me to keep my weight down and obesity is a big health problem. And so on......
This book is a fascinating insight into human nature and will help you understand both other people and more importantly yourself a lot better.