USE A SPOON
Maybe see a therapist? Some of them are really good and want to help. It won't always result in going to the hospital.
Try to throw eggs against the sidewalk or wall, hit a pillow, tear up paper, keep snapping rubber bands (it's a safer way), write a poem or just write down your feelings no matter how graphic they are.
Listen to music that makes you happy, draw, paint, read, do something that will distract you.
Drop the knife first. Go get plowed at the nearby watering hole. Buy the first beer for someone else.
Call a friend
Looks like you're asking this question a bit too late.
It seems that she's asking it JUST IN TIME ...duh!
Not if you look at her avatar :P
See a doctor.