Mild Manic - depression / bi-polar

Ever since I was in secondary school, aged about 13, I noticed that, when essays and projects were concerned, I was able to do large creative bodies of work only once every 3 weeks.
The fourth week was tremendous. I would be keen and have no bother coming up with ideas for paintings, stories and getting really high scores. The peak would then tail off to a slump of lethagy and despondency 2 weeks later and then build up again.
This wasn't such a problem with a project that could be delayed to a time when I could deal with it on a high point, but it meant that if exams coincided with a low point, I was in trouble.
Now, if I'm to do planning for teaching, I leave it until I'm on an uptick of the wave.  Same for coming up with ideas for novels.   Once they have been started I can keep going. If I have a break from them it's really hard to get back on board in a trough of the wave. The words per day follows the wave too.  I can get 10k done on a non-working day at the crest of the creativity wave, tailing off to 250-400 on a trough day.
At the moment I'm in a trough, but coming out of it.