I don't actually clearly recall at the moment how i feel after a meltdown. I can remember quite clearly prior to it simply cause its so distressing but afterwards not so much. What i can recall i'm not sure how to put into words...calmer, but also a low mix of tired/vulnuerable? I don't think i've ever felt totally calm like some of the above people mention, though. I don't like melting down and was raised to think that expressing such strong negative emotions was bad, and that doing so now would make me a failure so i don't even handle a meltdown well either. Whenever i melt down if i don't lash out in some way i end up hurting myself instead, on purpose. For some combination of release, control, and punishment.
I don't have them that often though, and usually violence is limited towards my poor laptop. I think the reason my harddrive crashed is probably cause i hit it all the time.

It turned out that one of the two regularly hit parts of the laptop contained the harddrive...so i try to avoid lashing out at my laptop now that it has a brand new one.
I'm more prone to shutdowns just by nature and how i was raised, but if i'm overly stressed out, have a lot to deal with, sleep deprived, that sort of stuff i'll have meltdowns. Its not fun. I've actually been trying to go to sleep at a 'decent' time lately so that i'll actually get the sleep i need to not just function without being overly emotional all day, but focus when i'm trying to do school work.