Not long ago, I recall someone speaking of fear. "From time to time we all feel a tinge of fear. It's what reminds us that we are alive."
And so it is with poker. I think it's only natural to feel a little bit of anxiety as the bubble approaches. The chips are sure to be flying as some of the short stacks make desperate attempts to chip up, while some players try to take advantage of the fear of others that are trying to stall and fold their way to a min cash. Big stacks are constantly raising to keep pressure or the short stacks. All-ins will be frequent among both the big and short stacks as they try discourage anyone that would hinder their attempts to steal blinds. And you yourself must often decide whether or not to play a hand or play it safe, whether to take advantage of a legitimately strong hand to try to increase your own stack, or to protect your stack and wait for the bubble to burst. In making these decisions, there is a hard learned lesson that must always be kept in mind, that the best hand doesn't always end up winning. There in lies the cause for being nervous at this juncture.
I think that nervous feeling should remind you to stay on our toes. Without it, you can become unfocused and miss important details that you should take into consideration in you decision making process. You might not differentiate between the guy who has been folding every hand for the last twenty-five minutes and the one that has been going all-in from the cutoff every time for the last thirty.
Take a deep breath and embrace that feeling. Let it be a reminder that you are still in the game. And not just in it, but in it to win it.