I forgot to mention something else that happens to me in the lead up to a show.
I start having dreams at night that I'm on stage - but the wrong one and the show is completely different. Or that I walk on stage at the wrong time and have to improvise to justify my reason for being there. Or I walk on stage and forget why I'm there.
Dreams like this really spur me on and they usually are a 'wake-up' call!
Nerves for me are a good thing - I'm more nervous if I'm not nervous.