Strategy for “Risky” Investments

So when you do allocate a small amount to “high risk” investments, at what point do you sell them for good or bad? Meaning what’s the actual % that triggers a sell? Fur example when Facebook was getting hammered last year I picked up some stock and when it went up like 30% (IIRC) I sold it off. Recently I gobbled up some HE stock and last week some BAC under the same premise.

I know every stock is different, but does anybody have done “guardrail” gains or loss percentages that they tend to follow?