Generally I would say no, I don't get nervous at all playing poker. I've played enough to feel confident in my own abilities, and have seen enough not to be too surprised at anything that happens. On top of that, I make sure to play within my means. So I know that no one tournament or cash game session is going to break me. This knowledge allows me to relax. When I'm relaxed I play better poker and when I'm playing good poker, it allows me to be more relaxed.