system
Given the following post, respond as if you're commenting on Reddit:
human
Why am I always depressed after “big” days?

Every time after celebratory events, family gatherings, nice trips etc I feel dead inside and need few days to pick myself up. Why is that?
gpt
I would like to hear the chemical science behind the phenomenon. We always call it "drop".

I figure it has to do with the high amounts of serotonin and dopamine released while engaged in positive activities with people you enjoy followed by the brain's withdrawal and rebound to baseline.