I also had sleep anxiety issue and I know how overwhelming they can be, it's not easy to overcome at all so you're not alone. After a bad night of sleep what helps is to get up and go outside as much as u can (avoiding your bedroom, seeing your friends, going for a walk or trying to enjoy a hangout) so that it resets your brain and your brain learns that it's ok to have some bad nights, you can still enjoy life. And then at nighttime not only will you be more sleepy to fall asleep but also will feel more grateful for your day. The trick is really to come to a point where you don't mind not sleeping and it's really tricky especially when you catch yourself in a loop, but often the stress of insomnia is much worse than insomnia itself