Dealing with nervousness in tournaments

I'm currently 1st of 18 in a fairly large (850 player) tournament. My hands are clammy, i'm breathing hard, and am generally nervous. I'm sure this will pass with time, but the first place prize ($650) kinda dwarfs anything else i've won thus far.

I realise this might sound silly to some of you seasoned pros, but is there any way of overcoming the stress of playing deep in tournaments?