An excerpt from here:
The market then, is not rigged against your investment success–you’re brain is. Every investor will look for patterns where none exist and blame the wrong people when it doesn’t work out. The same skepticism you show when a software salesperson comes into your office proclaiming to “improve productivity by 15%” will magically disappear when your broker calls. You will be sorely tempted to climb on market bandwagons late, after a huge run, because of a herding instinct perfectly adapted to the Neanderthal era. You will make important investment “sell” decisions based on the arbitrary price at which you bought the stock and you will fall in love with a current holding that is more likely to torpedo your portfolio than recover to book value. Your broker and the 1% are not to blame; they are just making it easy for you to do what your brain already wants you to.
More? A big list of behavioral biases.
Note: Shout to Ritholtz.com for the find.