When this tragedy hits, make friends with your nearest kleenex box, and go to bed, or to a room to cry. Don't try to put up a front, go to work, or help those around you. When you can't help yourself, you can't help others, any way. Take a day or two, to do nothing but feel your pain, cry, and get angry. Accepting your pain, is the first stage of letting it all go. Remember the act of grieving will help you to heal.
Talk to friends, or family, and a few days after the break-up go out into nature if you can. This is a nurturing place. Mother nature grounds us, and soothes us. Going for a walk in the mountains, by a stream, or the ocean, is a way to be alone with your thoughts, and to get grounded again.
At all costs, try to avoid the person who caused your heart to break. If you keep seeing them, it will just bring some hope to the surface, and that hope will be dashed on the rocks once again. Avoid more pain, by staying away from them.