Always have a stop loss in mind when you put on a trade. If you set a stop loss, and it tanks a bit while you're not actively trading, at least you'll probably be able to buy back in lower than your stop loss. So while you may have lost the original 10% (or whatever you set the stop loss at), if it dropped 25%, and you bought back in there, you're not too bad off. You've got another chance to make up the 10% you lost and then some.