You should have a plan for every trade you make. That means knowing why you want to buy or short the stock, where is a good area to place your buy/sell order, and knowing how much the stock will move before you sell. You should already know when to sell before you buy the stock. That means when to sell for a profit, or when to cut your losses. That takes all the emotion out of the trade because your trading decisions won't be dictated by fear or greed.