After some thought, I don't think "bored" is the state of not doing anything. Bored is the state of *being dissatisfied* with what you are doing (or not doing), and failing to generate any more appealing alternatives.
I think the wider issue has something to do with what conditions you need to feel alive, and deeply satisfied with being alive. I have a nasty habit of achieving something resembling balance (or contentment, or "enough"). But that's not enough of a challenge, and challenge is apparently something I am deeply uncomfortable without, so I go off and add one more project, responsibility, animal, commitment, whatever. Anything to make my life perceptually harder, because I'm hooked on struggle and overachievement, and suspicious of contentment.
I didn't know this until I wrote it down just now. Shit.