I used to struggle with this a lot, and still do occasional. The first step, for me, was realizing that I was a little bit sleep-deprived, and it was causing me to have anxiety as night approached. The catch-22 of course is that I couldn't fall asleep, and I would become twice as panicked knowing that the problem would get worse if I couldn't sleep. So step 2 was realizing that even if I am sleep deprived, I'll be okay. Your body isn't perfect, but if your exhaustion were to hit critical levels, you would probably fall asleep instantly.
But how can you fall asleep? There are methods you can apply once you are in the bed itself, but the before-hand prep is also important. One often overlooked way of falling asleep is to really tire yourself out. For me personally, if I do a ton of physical activity throughout the day, I won't even have the brainpower to be paranoid at night (And you get all that exercise as an added bonus!). The second thing to look out for (that you've probably heard before), is to try and avoid bright lights such as computer moniters/tvs/regular lightbulbs. That extra light tricks your body into staying awake longer than it normally would. If you absolutely must use electronics before going to bed, try to stick to softer light tones. Phone screens in particular tend to be ok, because they produce a different kind of light. A helpful program for your computer is called f.lux. It keeps track of the time of day, and adds a tint to your monitor that makes it easier on the eyes as night approaches.
Now let's talk about once you are in the bed itself. These could all be hit-or-miss, but try them, see what happens. One thing that definitely helps add some order to your routine is making your bed sometime before getting into it. Not only will it be more comfortable, but you are exercising control over your environment, which can help you relax. Once the lights are out, sometimes the silence can be deafening. Lots of people (even those without anxiety issues) like to have white-noise as they fall asleep. An electric fan can do the job fine, but there are some more expensive white-noise machines if you want to go that route.
My last tip is more of a personal one, and I'm not sure if will be as useful: I started looking forward to my long hours awake as time to daydream about things with no real-world impact. For instance, I'll pose myself a question, "What would I do if the zombie apocalypse hit tomorrow?" Just keep in mind that the question shouldn't be something that stresses you out. If planning for the apocalypse isn't your cup of tea, maybe plan out your dream-home, or your crazy idea for a video game, or even dream up an alternate world. Eventually you might look forward to the night as well.
When I talk about these things, one song that keeps popping into my head is the original "Sound Of Silence" (https://www.youtube.com/watch?v=4zLfCnGVeL4), with its opening line "Hello darkness my old friend".
I hope these tips help, I know they did for me.