Almost happened to me. January 1st a few years ago, decided to try the gym for the first time on a guest pass with my sister. Didn't realize I should have adjusted weights. Fainted 3 times ( by the weights ( squat rack ) and then twice in the bathroom. ) If I wasn't vomit phobic and mind-over-matter'ed it, I would have puked too as I was gagging.

Shit happens. And more often than you think. Be more careful, hydrate, don't push yourself too hard, and eat something solid beforehand.