Help with a Wandering Mind

I have a serious problem becoming lucid in that I cannot sleep unless I am so exhausted that I pass out immediately, which is not condusive to REM sleep. I rarely dream at all, and becoming lucid, try as I might, is getting more and more difficult as time goes on. (Note that I have done it on several occasions, though I'm still definitely an amateur)
My problem is that my mind wanders - and goes to very, very dark places - when allowed to roam as it would if I disengage from stimulation long enough to begin falling asleep. Does anyone know a way to keep the mind from wandering while trying to fall asleep? The thoughts range from philosophical questions - what happens after death, etc., which panic me very much as there's no way for me (or anyone) to know and I'm a tad bit obsessive when it comes to knowing everything - to things like imagining the potential death of loved ones, the end of the world, etc.
The point is, unless distracted my mind goes down dark roads which keep me from sleeping, but distractions like video games and books will also keep me from sleeping.

Try writing in a journal. You can do it before bed or any time during the day. It can be on paper, on your computer, an app on your phone, or whatever is convenient and private for you. When writing, just let your ideas flow out whatever they may be. It seems so simple and bland but trust me it can be very therapeutic. It's not a distraction like those other things you mentioned, but rather an outlet for you to collect thoughts and release tension. When thoughts are spinning in your head, they tend to linger and repeat unfinished. But when you set yourself to write them down, you engage a different part of your brain that finds continuity and progression in the thoughts. After writing, it still might not make any sense but the process of writing makes new connections and untangles the repetitive loops.

If you find it difficult to form the habit, try the 5 minute rule. Commit just 5 minutes to writing. You can spare just 5 minutes, right? If after 5 minutes you want to stop, okay. More often you'll find you want to continue a bit longer. Start with this: "Dear Journal. Today is Monday." (or whatever day of the week it is). If you don't have any big thoughts at that moment, just write a few sentences to summarize the mundane events of your day. Another good topic that you can always write out is your dreams from last night and what you'd like to dream about tonight. Some days that will be all. Other days you'll find the desire to writing on deeper topics.

First of all, if your drinking things with caffine in it, then good luck. Caffine stimulates the mind, so stop if your drinking caffine.

You could try something called, "Sleep Whisperers" on youtube. It's basically people who try to help you get to sleep, but speaking slowly. Try to slow your mind down and believe me, you can.