Since we are talking about intraday trading, if you dont sell your shares by 3pm, they will be squared off automatically by 3:15(in case of my broker, it varies). And to reply to the first part of your question....,"but the price goes down. so why do people see their shares as soon as it goes down. why are they making a loss? why cant they wait till the stock goes up?".... Waiting for a price to go up again also leaves your position open to severe draw-downs. Risk management is of the essence here, which is why most traders have a predetermined stop loss as a part of their exit strategy.