I'm not sure if I'll be able to explain this well, but I'll give it a shot. I can have the same problem you're describing, which can keep me awake for an hour or more. However, I've noticed that when I finally start to fall asleep, the same thing happens every time: I let go. I don't engage in those thoughts anymore. They still come, but by not indulging in them, by not engaging my critical thinking processes to analyze these thoughts, to worry about them and follow them down a long and wakeful chain of imagined causality, they tend to start to form the beginnings of dreams. Instead of being purely intellectual, these thoughts begin to resolve into imagery and sound and rudimentary plot. Often it's just an acting out of the thoughts that have been plaguing me - if I'm worried about a particular upcoming event, that event will begin to play out behind my closed eyes. And as soon as these images start, I just lie back and watch - turn off the mind and turn on the imagination. What keeps you awake is thinking, so if you pretend as if you're just lying down to watch a movie - something which is passive instead of active - you'll be in a mindset more conducive to sleep.

So basically, just let go. Let those thoughts come, but let them go as well. Just watch. Acknowledge them and then dismiss them until one begins to take hold in the imagination. When that happens, pay a relaxed attention to the developing dream. Don't try to WILD - if you're already having trouble getting to sleep, WILD and even MILD will require too much thought and attention and will dissolve the dream and keep you awake even longer.

I don't know whether that makes sense to you - I hope it does, and I hope it helps. Losing sleep because the mind can't let go of waking worries is exasperating, so good luck.