Writing protip: get a keyboard, open up your word processor, and get in bed. If you can touch type, you can write with your eyes closed. It's SUPER comfy.

If you have an idea for later, just make a note in-line with bold or [[[SOMETHING EYE CATCHING]]] or "asfdfjfj" (i.e. something that triggers spell check so you'll look at it later when you're proofreading it).