With me, it includes a lot of hormone/testosterone fluctuations. The next day might be great, or it might be terrible, or might be nothing at all. I might have tons of energy and be horny as hell, I might have nothing special happen, or I might be on the verge of a frickin coma and feel like the universe is literally tearing me apart on each of the physiological levels (physical, mental, emotional). Totally random. I guess at least I don't have a boring life....