Draw down table.

These stats are popular in trading publications but they are worth repeating:  A 5 loss is easy to overcome, a 10% loss can be overcome.  After that, things look pretty dark.

Drawdown	Gain to Recover
5 Percent	5.3% Gain
10 Percent	11.1% Gain
15 Percent	17.6% Gain
20 Percent	25% Gain
25 Percent	33% Gain
30 Percent	42.9% Gain
40 Percent	66.7% Gain
50 Percent	100% Gain
60 Percent	150% Gain
75 Percent	300% Gain
90 Percent	900% Gain