Throw your face into the bucket full of ice and water. Leave it there for predetermined times based on physiology and psychology. 15 Seconds first, to get your lungs to work. 20 Seconds next, after getting used to holding breathe. Try for 30 Seconds last, that is what they tell me. Then I go for personal bests to make the pain even worse.
Ice Diving is a coping skill for cutting. It's a way to induce pain without really harming yourself.