Not sleeping. Or getting by on little sleep but not missing it. Say maybe 4 hours or less per night (though to stay stable, I've really got to have at least 6, ideally 8 hr./night). If I have 3 or 4 nights with that little sleep, full mania will be right there. It happens fast for me. Even though hypo feels so good, once I realize I am in this pattern, I call the pdoc. I hate to end the hypo, but the full-blown mania has been nothing but trouble for me and my relationships with others.