i find that nerves makes you more alert and spontaneous.
im a bass player and have played gigs were the more nervous i am before hand the more my playing benefits from it.
i have played runs and licks that upon listening back have sounded like some other bass player , in other words , you can impress yourself.
saying all that , once your on stage or doing what you do , it all goes away and you can control that pre nerves and turn it into something creative