Yeah, first time I properly smoked weed on my own (ages ago, this is), I think I seriously over did it.. my mouth was stupidly dry, my heart rate soared ridiculously. This made me really panic, thinking i was going to have a heart attack and stuff :|

Nothing like that since then though, I guess it's 'cause I was a novice.. Hmm.

And your heartbeat will speed up a bit when you're high regardless. It's to do with venular dilation, lower blood pressure and all that shit.