I've often read that is a correlation between bipolar and starting up a company: "the highs are higher, the lows are lower." (Which tends to cause which is academic.)

Here's what I've discovered: the highs are far more dangerous than the lows. The highs are good, whether they're based on real-world success, or your invisible fuel, the die-hard belief in what you're pursuing. You need those highs: milk them for all their worth.

But what goes up, must come down. Whether based on a real setback, or a stray negative thought, it doesn't take much to send you back down to earth, or straight through to hell. When the confidence evaporates, suddenly those unpleasant realities you were dismissing all hit you at once, and it's too much to deal with.

Everything you mentioned is great for riding out depression: sleep, a good meal, exercise, relaxation. You've got the treatment covered quite well. But after you bounce back, pay attention to that "winning" feeling, and work on moderating it to just the level you want, so that it can burn for longer, and you have less far to fall. Keep spending time on basic human needs, even when you're on top and you feel capable of 18-hour days.

Ideally, you want a steady engine, not bursts of up and down. But those will still happen sometimes; roll with it, forgive yourself, ride it out, and keep moving. Good luck!

(This is just a bit of awareness I picked up about myself; your mileage may vary.)