you know every person trades to get profit but all can't get at the same time some one have to loose so that other can gain. when ever you are trading in shares just make a flow chart of the price per share if you have bought that share on like 500/ share and the price is going on 480/ share at that time if you think that share price will rise that just made a purchase on 480/ share and even if price didn't rise and it was stuck on 490/ share than you can sell to recover the loss from 2nd transaction.