Ask HN: Is anyone else phasic in their productivity/interest?

I've noticed when I work on my apps or when I become intensely interested in my martial arts training, that I will be very productive in a 6-8 week sprint where I'm excited to work and the hours fly by and I'm constantly thinking, studying and reading. But after that period I would gradually fall into a similar 6-8wk lazy period, where I maybe put in 2-3 hours for the day, and I don't feel like working and don't think about it as much. Until the the next phase comes around, and I'm riding high again.

It sounds like my low phase is just a product of my excitement high wearing off, but when I'm in the lazy period its very difficult to be productive and motivated. I don't know if there is a net benefit from this balance.

Is anyone else like this, or are you more controlled and averaged?