I agree your mind doesn't stop, but sometimes I solve my problems in that moment before sleep, I think because I can direct all my energy to it (even eyes are closed, so no visual processing needed).

Though the tired mind is often very keen to simply recurse over thoughts you've already had opposed to think of new ones. If you find you can't stop yourself going over the day though, then 10-15 mins of meditation, where you force yourself to concentrate on clearing your mind, can stop these thoughts so you can sleep. Do this every night for a few weeks and it becomes second nature.