Euphoria and depression go hand in hand as we, if we’re so inclined, pass around the circle of life.
First I had one of my euphorias. It was probably brought on by a year’s worth of stress. The last straw was being unable to force myself to have a viewpoint character doing physical violence to other characters in a story I was writing.
A fine insight you might say and I will agree with you. Another was the instant understanding of the difference between writing from the head and writing from the heart. A good story is under construction as a result.
But how does euphoria follow from that, you're wondering? I don't know. In three percent of us it does apparently. I go into a cognitive dissociative state, a trance, and my unconscious generates extreme bliss. With no help from any drugs.
But the higher I go in the euphoria, the deeper the depression afterwards takes me. And where the euphoria was a wonderful eight day event with two or three days to recover, the depression is, so far, a three week marathon and for some inexplicable reason, far more difficult to walk away from.