Write it all down.

What do you need to do? What do you want to do? What things don't really matter to you?

Organize it on paper or whatever medium makes sense. I like OneNote and Trello. I've found its one of the easiest ways to remove those thoughts from the back of my mind is to put them someplace actionable and consistent. A stream of consciousness todo list isn't very productive.

With regards to instapaper or readability, either:

a) Treat it as a bookmarking service, not a read-later service. Then reference it when a topic comes of importance to what you wrote down above or you're just bored.

b) Clear out all 800 articles and start over, possibly being more selective or auto-clearing them monthly.

These are both things the brain does naturally, pruning through attention and focus and long-term storage for future reference :)

EDIT: Formatting