Basically, “Try Not To”. As the author of this article proves well below. 

Warren Buffett has commented that he would have more money today if he had never sold a position. Perhaps a more simple summary comes from Tom Gayner, the very successful chief investment officer at Markel (NYSE:MKL), who has said that investors make more money from their butts than their brains (as in, sit still and don’t overthink things).

Reading a well written article on the topic of “selling” from time to time is usually a valuable expediture of any investors time. For most of us, if not all of us find it difficult & even downright terrifying to sit through a correction in either a market, or an individual stock. The temptation to sell at the wrong time is powerful – Editor Money Talks

….read When Should You Sell?