I occasionally get those bouts of racing pulse/pounding heart, usually accompanied with clammy skin and low blood sugar and associated with low blood sugar from eating candy at the wrong time, although i may get them it sometimes independently from consuming extra caffeine, i haven't really kept track well enough to be sure.
But the racing heart caffeine/candy overdoes thing never triggers a panic attack of any kind. I'm just like, hmmm, my heart seems to be going a bit strong, that's annoying. If it's due to low blood sugar i'll feel crappy at the same time but only physically, not in any emotional sense.
I have no idea if that's normal or if i'm some kind of exception, but it certainly makes me very happy. Real panic attacks sound like a pain in the ass to deal with (to understate things a bit.)
I certainly seem to be exceptional (in the literal sense) in caffeine totally failing to keep me up at night, and at least somewhat in my ability to sleep when i want to and deal with sleep dep pretty well when i don't want to. And i've never gotten a hangover in my life (though that may just be because i get tipsy so easily that i never drink enough to trigger one.)
It's nice that there are some little things that make my life more enjoyable. Of course there are plenty of ways in which i'm not so great to make up for it, and it's a little depressing to think that most of the good things about me are just things i inherited and i haven't ever really achieved anything significant on my own, but i'm trying to keep this positive :) Besides, consumerism may get a bad rap, but the world needs at least a few consumers, otherwise who are all the artists going to be creating stuff for? :)