There are many important considerations for when to sell a holding, such as trend lines, trending swing highs and swing lows, volume patterns and price/volume support and resistance areas, not to mention the changing fundamentals, or perceived changes in fundamentals, of both markets and individual equities. What should never be considered is how much profit is in your pocket, because this cannot possibly effect what's going to happen next in the market, and our one and only job is predicting what's going to happen next in the market. Profit targets in general are inconsistent with the principle of following the tape. 
 
That said, because of natural volatility in the market, when we use our normal buy signals, we have found that small moves up can be reliably achieved and larger moves are much more likely to suffer intervening pullbacks which inherently present the danger of larger corrections. Therefore, we are often quick to exit a trade with small profits, simply because larger moves are so much less common. We will usually wait for some sign of the likely end of a rally, however, before pulling the "sell" trigger.