When insomnia starts to get out of hand, I like to force myself to stay as alert and awake as possible until I can’t do it anymore. Usually a single totally sleepness night, carried through to the next day, around 48 total hours of wake time, is enough to get the mind to let go of whatever it is that’s causing it to run itself crazy.
Another thing you can realize is that it’s not a race. You’re not going to ‘get there’ any faster. If you keep telling yourself that there’s a good chance your mind will eventually accept it.