Every situation is different when it comes to timing a sell order. Short term stock gains are taxed at ordinary income rate. Long term ( over a year held) are taxed at 0%, 15%, 20% depending on income amount, with majority falling into the 15% column. You may need to or want to offset a gain with a loss. I sell some short term if I feel like it may drop more than the difference between short term gains and long term gains. Some money costs you more money waiting for it to come back, vs. Investing it in a stock that is gaining at a faster rate.