A rational person should keep those shares most likely to appreciate in the future while selling those likely to depreciate. Indeed, this is what you must do if you are attempting to maximize your financial return. The stock market rewards those who buy low and sell high. But we are actually more likely to keep the shares that have lost money, regardless of their future prospects. Why? Because we hate to crystallize a loss. The moment a losing stock is sold, a paper loss becomes a real loss.
