An excerpt from the US Army Survival Manual:
The greatest enemies in a combat survival and evasion situation are fear and panic. If uncontrolled, they can destroy your ability to make an intelligent decision. They may cause you to react to your feelings and imagination rather than to your situation. They can drain your energy and thereby cause other negative emotions. Previous survival and evasion training and self-confidence will enable you to vanquish fear and panic.
Fear and Panic destroy your ability to make intelligent decisions.
They are also the greatest obstacles to surviving the financial markets.