The Simple Pleasure of Taking Notes

I'm not sure of the causal direction, but my mood and productivity both seem to shoot up whenever I take playful notes throughout the day. Here's how I do it:

1. I always have a pen(/pencil) and 3x5" notecard on me.

2. One side of the card is for to-dos (i.e., don't go to bed until you finish these N things), and the other for observations, questions, funny quotes from professors, books I should read, things to write about, etc.

3. When I'm bored or at least once at night, I go through the day's notes and (a) act on the easy ones, and (b) put the idea stuff in a text file for later.

I find that having a simple way to take notes keeps me on the ball and intellectually engaged. It may be a bit weird to whip out a note-card in public, but I've found that tons of stuff I didn't think was worth jotting down ends up being a gold mine later on.