I think it's really important to realize how much of a vulnerable position sadists are putting themselves in when they participate in pain play. This is particularly important in established relationships, as opposed to casual settings, but important in both nonetheless. Also, this post is strictly addressing participants of kink who practice it responsibly and care about their partners.
When sadists do pain play they are having to grapple with the fact that they get pleasure out of causing pain to someone who has put their trust in them. This can be devastating if they feel as though they have in any way compromised that trust. Especially since even people who know about aftercare and try to do it, often overlook the aftercare that sadists, or even dominants as a whole, need. I imagine this happens a lot with pain play scenes, as so much emphasis is placed on taking care of the masochist. Obviously, that's important, but it should not be one or the other. The point I'm trying to get at is this:
Masochists/subs, please remember to give your sadists/doms aftercare. The biological and psychological functions that cause subspace and subdrop can have the same effect on doms. Doms are just as capable of experiencing that rush of adrenaline and endorphins, and just as capable of crashing, once the scene is done. Tell your sadist that you still trust them and feel safe with them. They need to hear it.
Sadists/doms, please remember that there is nothing wrong with having sadistic thoughts and feelings if you're acting them out in risk-aware and consensual settings/dynamics. I think I speak for all masochists when I say that we are so thankful for sadists who participate in responsible kink. Remember that there's more to aftercare than just caring for and comforting the sub. You deserve to be reassured and to receive the care that you need.