One thing I discovered, accidentally, is that it's possible to train your brain to switch off by associating certain thoughts with sleep. Start thinking of something pleasant and dreamlike, anything at all, as long as it's fantastical and like a dream. Find one that's your favorite, and then stick with it, every night. In the short term, on the very first night, it'll help you get to sleep eventually because it'll get your mind off of that pointless treadmill of left over thoughts and feelings from your waking day. In the long term, once your brain fully associates that thought sequence with sleep, it'll just start shutting down automatically when you initiate it, and you'll pass into sleep very quickly.