Something I've always noticed and am going through now. Sometimes I'll drink too much the night before and be concerned about a hangover the next morning. Morning comes, and almost always my first thought is "gee I feel like shit but actually this is way less bad then I was expecting" this misplaced optimism gets washed away at an indeterminate length of time later when a wave of awful nausea crescendos to a peak of crappiness before gradually receding leading me to think "maybe that was the worst of it" only for the cycle to repeat.

This happens even when the hangover is not one severe enough to have caused vomiting. Feeling sick from drinking too much I understand, but I wonder what's physically happening during the peak of these waves that's not happening during the troughs.