I've had this sort of problem, more-so in the past than nowadays. But even nowadays, every so often I'll go to bed. Sometimes I'll go to sleep & then wake up a couple of hours later. (I wake up a lot 'cause I have to pee.) Or sometimes I just can't get to sleep at all.

Anyway, on some of these nights, I'll get some grandiose idea in my head and I just can't stop thinking about it. Pretty-soon I'm building castles in the sky, as the saying goes. Years ago, I used to fool myself into thinking these flights of fancy actually had merit. Nowadays I know them for what they are and at least don't get caught up in them even if I can't actually stop them until they finally just wear themselves (and me) out to the point where I do finally fall asleep.

Nowadays I'm on Clonazepam (not recommended), not for this concern but for other issues. (Still, the Clonazepam helps with this problem too.) But pre-Clonazepam one thing I used to do, when I was in one of these "mimi-manic" states as I like to call them, was to get up and walk around our dark & quiet home... sort-of a walking meditation, if you will. Sometimes I'd walk for as much as an hour or even two. I'd lightly focus attention on my feet as each foot touched the floor. I'd hear the sounds of traffic & trains off in the distance, the sounds of wind or rain if there were any. I actually quite enjoyed doing it and sometimes miss those experiences. (Once in a while I'll still do it. But it's typically for shorter periods of time.) And typically, once I finally went back to bed, I fell asleep.

You mentioned you meditate. If you're presently doing sitting meditation, developing a walking meditation practice might make a nice addition to your practice. Personally, I think one of the best sources of material on the practice of walking meditation is the books of (the late) Thích Nhất Hạnh. (Highly recommended.) Best wishes...