I had my second Moderna dose yesterday, it's been 24 hours, and I think I'm done with side effects, so here's my story.
I got my shot around 9am. Until about the 11-hour mark (around 8pm), I had no side effects except a sore arm, but at that point I started getting chills and an achy neck and shoulders. I used a heating pad on my back for the rest of the evening, and it helped tremendously. I got tired early but only went to bed a little earlier than my usual bedtime, with lots of blankets, the heating pad, and a couple of purring cats (they are so good at healing energy!). At that point the side effects were more annoying than they were serious.
Overnight, the chills went away after a couple of hours, and I turned off the heating pad, but I still didn't really sleep well. Lots of waking, repositioning, trying to get back to sleep. Woke up with a slight headache but still nothing major.
Then around half an hour after I got up, I had a huuuuge wave of nausea and dizziness. I sat down and passed out. It was way more unpleasant than anything else that had come before, but it only lasted about ten minutes. After I recovered, I got up, and — knock on wood — have felt totally normal since then. It was almost as though instead of giving me drips and dribbles of side effects, the vaccine decided to give it all to me at once. It's been two hours since then with not even a stiff neck.
In terms of self-care and side-effect mitigation, I just followed my usual routines. I'm a big walker (hit my 10,000 steps yesterday, which is a little over four miles) and a big hydrator (about 108 ounces; my usual goal is 104). I'm 44 and am generally very healthy. So my side effects lasted about twelve hours, but aside from the debilitating nausea that preceded the fainting, it wasn't that bad.
ETA: My blood pressure is already at the lower end of normal, and an additional drop in blood pressure or blood sugar probably combined with the more typical side effects to cause the fainting spell. Fainting is not a normal or "known" side effect of Covid vaccines; the few instances that have taken place are typically at the time of injection and are attributed to fear of needles or pain. Mine was almost 24 hours later, and I don't have any relevant phobias — nor would they have made a difference at that point if I had.