Had my second Pfizer shot on Sunday at 11am. Easy, just like the first. Barely felt it. Since I had no side effects that time other than a sore arm I wasn't worried at all.
Went and played golf in a 16-man tourney (and won lol), had beers after until 7pm, and then had my cousin over to chat until 11pm.
Suddenly felt very tired... then the shakes started. And within an hour I was in full-blown flu mode. Hot flashes, shakes, muscle myalgias, joint pain, dull but constant headache, and some nausea. Not fun. Got to sleep around 4am but couldn't go to work the next day and slept in all day - just fucking exhausted. Still felt bad yesterday evening but woke up this morning with nothing but a bit of residual tiredness and a slightly sore head.
Looked it up online and apparently these side effects are much, much more common for the second dose. That said, at least I know it was working!
So bear that in mind for Pfizer. You may have a rough 24 hours starting 12 hours after the 2nd dose. The first couple hours are the worst of it, then it trails off quickly enough into more manageable symptoms. For info purposes, I'm 37 years old, 6'1, 177 lbs, no health issues or allergies, but not physically fit.