Anything to get those thoughts out of your head for a little bit, food, exercise, focusing on a hobby, watching a movie, or a show you like on tv as have already been suggested are pretty good ideas. Something that you can enjoy even in the slightest will work, to enjoy the moment because that's all you really have.
If you want think of someone you know maybe even someone you only know online(through SF) and send them love and kindness, wish them happiness.
Best of luck.