anxiety
"I have social anxiety & knew I'd literally fail out of grad school if I did not do something about my immense fear of public speaking (when my Social Anxiety is at its worst). I'd have a shaky voice, dry mouth, nausea, my heart would race and I would be physically shaking. Knowing those physical side effects would happen just made me more nervous and make it even worse.  I take one of these an hour before my presentations now (and only when I have a presentation, like every few weeks, it's not a daily thing!) & it *definitely* lowers the physical effects so I can get through it, though I still get (way less) nervous. I only get a slight shaky voice, but my heart does not race, no dry mouth, nausea & I don't shake. It was honestly a life saver for me."