Case 1. - You're worried about something, how it will turn out, what will happen etc etc. Case 2. - You're with someone you like and you're afraid of what to do, because you like them so much (I've experienced this ;])
Remember that song, "I am watching you"? Well, that's what it's all about. There you are, up on center stage, 50 to 100's of eyes on YOU. Is your hair OK, what about your suit or your dress, are you...
I took the shot after my first born and was a wreck. Everyone thought it was post baby blues, but it went on and on. The shot last 3 months, I did it twice. I would never do it again. Our hormones...