i don't really get sweaty when i give presentations, my legs just get super shaky or my fingers start to twitch. i had it the worst when i did a poetry recital competition and my legs were so shaky after i recited my stuff that i was worried i'd trip on my heels getting off the stage and hurt myself.
i'm sure it's probably a normal thing to get nervous reactions even when you don't feel nervous about giving presentations. i'm not that scared/nervous about giving speeches or presentations but i still get nervous reactions.
holy forget 20 minute presentation
no wonder you went waterfall mode
i've had to teach a physics lesson to a bunch of 9th graders before. my class periods are an hour long. i'm glad we don't do the whole student-directed lessons anymore, they're way too stressful and you get a better education when an actual teacher is doing the teaching.