prepared nervousness 

when you are waiting to do something with the sudden urge right before it happens to not do it

1)
"I really want to go to Dreamworld tomorrow, but I don't know about going on The Giant Drop."

"Don't worry. That's just prepared nervousness."

2)
"When Sam was about to kick Tim in the balls, I thought he was suffering from prepared nervousness."

prepared nervousness by Kamikaze Watermelon December 16, 2008