Exactly. I have some depression (or maybe just standard human psychology that I have somehow failed to cope with) that will flare up horribly if I'm not eating

Exactly. I have some depression (or maybe just standard human psychology that I have somehow failed to cope with) that will flare up horribly if I'm not eating well, exercising properly, getting enough sun, spending enough time not working, getting enough social time, and probably a few other things I have no idea about yet. Left to my own devices I'll end up eating out for all 1-2 meals a day, only move from the bed to my car to my desk, forget what sunlight looks like, pull 12 hour days and 4 hour nights of sleep (or stumble into a 48 hour cycle), IM only my closest friend every few months, get suicidal and quit another job because nothing matters and the world is cruel. For me at least, quantified self is not about trying to treat myself like a machine, it's about trying to remember not to.