The best way to stop thinking about something that is sad and distressing, is to bombard your mind with other things. Try reading a good book, it will make your brain have to focus on the details. Listen to some good music. Cook a nice meal for yourself. You will be actively doing things with your hands and other senses, making it difficult to think about what is upsetting you. I really do hope this helps you out and best of luck in your difficult time.
Think of something happy... That's what I'm trying to do cuz i keep thinking about my ex boyfriend I know pathetic but just think of happy memories and or go get something sweet to eat but don't eat your pain away cuz that's not a great idea..(:
There have been geniuses that construct houses in their mind. They have items (memories) they lock away in different rooms until they need them. It works... I have things that make me sad. I have boxes in my mind in the cellar that have names on them. I put those thoughts in the box, whenever I start remembering something I concentrate on that box instead of what's bothering me, and it relieves... some of the tension.