When the intensity and duration of extremes are tolerable. Given moments, can be very uncomfortable, but not persisting and pervasive to where it really messes with my functioning.

That's my usual take on it anyway. Sometimes, it goes one better in that there really aren't (even short-lived) intensity bouts to deal with. By this I DON'T mean flat emotion. The intensity bouts mentioned above are very negative for me --as in suicidal or very self-destructive energy level, NOT as in deliriously happy, or deeply moved. Those are just fine.
But there's just too much precariousness to my life to wait around for that level of fabulosity, so I count the other. It's simply more realistic, given my overall life situation.