Personally I have found the cure to not being able to sleep, sleep anxiety, insomnia having suffered these and tried absolutely everything. Focus on your breathing (constant and smooth rhythm), and when you get distracted, focus again, and keep doing that until you become good at if. If you remember when you were younger and slept like a baby, all you did was breath until suddenly you don't remember falling asleep.
This has worked 100% for me. The only issue I have is choosing to sleep early, which I'm working on too. My self-discipline sucks!
I believe all cures must be of a natural origin, otherwise, we become reliant on something. And when you take away that something, often the problem comes back because we haven't cured the problem naturally.