Don’t play when mad, sad or generally in a bad mood.

When you play poker, you shouldn’t do it to escape from being depressed or having a really bad day. You start out on tilt — playing emotionally, not rationally — and you won’t play your best. Likewise, if during a poker game, you lose a big hand or get sucked out on and feel yourself going on tilt, stand up and take a break until you feel calm later on. Fellow players will sense your mood and take advantage of it.