Value Investor's Mistake De Jour

The most dangerous downfall of a value investors is falling in love with a real bargain. The so called deep value investing can be the biggest value trap of all.

Many people don't know how to see and analyze their own mistakes. The method is simple. Take a look at your biggest stock market losses, and post here the causes of those big mistakes.

I will start:

Mistake 1: Borrowing too much money.
Mistake 2: Buying cheap low quality stocks that you don't understand and watch them go all the way down.
Mistake 3: Paying a seemingly low P/E for peak earnings.

What do you think? Can you share insights about your biggest mistakes?