I've actually just thought of something this morning that might make a difference. Rather than just control your thoughts, try to be a bit more aware of you body. At least, do so when you are very relaxed and are starting to feel a bit numb from lying still. Try to notice how heavy it feels, what mild sensations are there. This should also help with inducing heaviness.

I haven't tried it out yet, it's just a hunch. I'll edit the main post if it proves helpful. Feel free to try it out if your timezone is ahead of mine.