That happens to me a lot. listen to really depressing music, talk to your friends, talk to people with worse lives than yourself, phase out, just lie there thinking, these are all methods I use, however they only work sometimes. Sometimes it helps just to lie there and not think and to just cry. If you want to resist the urge sit with your family. They'll either severely depress you so you can't resist the urge or make you forget it completely.