Probably the most important one is to always use a stop loss and respect that stop loss no matter what, whenever we make a trade we want to earn money, no one ever makes a trade with the intention of losing, but since we are not perfect then some of our trades will lose, however many prefer to keep holding their trade with the hope it turns around and that is when catastrophic losses can occur, it is better to accept defeat and wait until the next profitable trade appears than to risk losing a great deal of money over a bad trade.