Get out of that losing trade if you are still in it, stick to your safety net rules and ignore your account balance! Continue to trade as if it was just a regular stop loss hit. In trading it is all about preserving emotional capital and remaining in a position of strength so that you can seize fresh opportunity ahead. Treat such a loss like a failed exam and simply keep studying. If the loss was huge it also helps to take time off the markets. After a couple days/weeks the joy and passion should be back and you should be eager to improve. If you truly stick to the safety net rules chances are very slim that you'll ever experience a huge loss. If you blew your account, save up another stack if you still feel the passion, if not leave trading alone.