I'm sorry you have such a hard time with racing thoughts. They can certainly ruin a tired mood when you could really sleep, but are instead just tortured by a bunch of remembering and "what ifs". I have a sorta goofy tactic that I use (and is mostly successful): when I cannot get to sleep right away - this is most nights - I try to think of something really complex that will require all of my attention; like I may try to do a bunch of difficult math in my head, count by 43s something really hard for me OR I will try to only think in another language (I use French since its the only other language I know). Anyway, most of the time this is usually successful after about 20 - 30 mins. I know it sounds lame, but it does a great deal towards quieting my mind down to just ONE set of thoughts instead of a zillion things that remind me of a zillion more that all keep me from resting.

I hope that was helpful.