Nothing wrong with a bit of nervousness, although I try to keep it within the realms of anticipation rather than outright fear.
Its funny, but the best thing to calm my nerves is actually a wait at the hold prior to departure, which happens reasonably frequently at my home field. Whilst it is a bit of a shag seeing your money disappearing down a plughole, I find that once you have got all of your checks out of the way and you are sitting there with the engine nicely chugging away at 1200rpm it can be quite serene...