My mood swings vary and for many years I took it as a foregone conclusion that I was heading into an emotional nosedive if my mood dipped. Yes, there are patterns to my moods and most of my serious depressive episodes have occurred in (roughly) two yearly cycles.
Throughout the day, every day, I have peaks and troughs - sometimes I feel content and happy, other times I feel like an emotional zombie. But these feelings pass and then I move into the next moment. I'm getting better at seeing the signs.