Nerves are a normal part of punting. It is the thrill of something new. My first punt I was a quivering wreck until I saw the girl for the first time, then it became excitement instead.
My next few punts afterwards were still punctuated by nerves. I always had to have a pre-punt shit before I left the house.
A number of things get the adrenaline going still, calling a new girl for the first time, trying to find her place and getting in and out without detection. Add to that the ideas running through my head of the sort of things that I could be doing with her, and it all comes together for lovely feeling of anticipation, not quite as feverish as going to bed on Christmas Eve as a kid, but something along those lines.
If I am honest, that naughty excitement is why I still punt and it is one of the reasons why I leave big gaps between punts, I don't want it to disappear from being too used to it.