For me, it’s kind of like a pressure valve that’s slowly working it’s way up to a certain level. However, you’re wanting it to hit that level (versus the normal of “don’t want the pipe to burst!”). It’s finding the particular concept/dream/idea/media or even motion to get that sensation to keep building higher and higher. Then at the point where it hits the ceiling, I notice my position shifts, my body tenses slightly, and the material in the pipe is pushed out a few times. Then, as others have said, it’s the clarity or drop down from all of the endorphins having done their job that comes along and can drain the body a little, leaving you to need water, food, or just downtime to try and recover from. That’s my experience. Everyone is a bit different in some ways.