symstym

I've found that it's really useful for me to write down my thoughts. In the past I assumed that I would remember any worthwhile ideas, but I've found that's not the case at all.

When I'm not at my computer, I use iPhone Notes (about to switch to Simplenote) for short notes and a small notebook if possible when I want to do serious brainstorming. When I'm at my computer I usually use a personal MoinMoin wiki (MoinX). For todo lists I use Things on my iPhone and laptop.

I second this. I can't relate the the part about a sense of security, but I've found that it's very important to "take care of myself", in whatever form. For me that often means cleaning my apartment, taking care of business I've been procrastinating on, etc. Those are concrete, actionable tasks that are guaranteed to make me feel better, even if only a little bit. At work, I similarly try to focus on specific small tasks if possible, to keep my mind off of things.