Doing so much stuff on the spot has helped my playing incredibly, and has also helped me build a reputation as a guy who can do just about anything at any time. Also, I think anyone who can get up on stage with 2-4 guys they've never met before and make a song up is in a good place musicly. But confidence is a must, have to have the attitude that their's nothing you can't work around, or better yet, work with.