How do you stay cool during a game?

Whenever I start playing a game, I start to get nervous. My brain starts to heat up fast that I blunder a lot of pieces. So how do you stay cool? Is there some kind of psychological trick? Thanks for your time.

Sit on your hands.

Then use our feet to move the mouse.

Join the army. Best an elite unit. They will teach you.

You'll get rid of it after playing many games here, i too had your problem!

I am a kid. 

Even after playing many games, my brain heats up! I have a problem I guess..

You just worry because of the clock running low  try some bullet games, it will go away maybe

It is not about the clock actually. It is about the opponent. The position he plays look really complex when in fact it is easy.

The image of the position freaks me out , that is what.

Just know that you're gonna lose anyway of you're opponent is significantly stronger than you. Keeping that in mind, your opponent is worrying about getting defeated.

Just wait for @IAMBBW to say you're welcome for the "Thanks for your time" line... But anyways, listen to some songs and ..... well I don't get nervous, so I can't give much.... maybe use your hands to think about the game and use your nose to make the moves

usually i use air conditioner so i can stay cool during games

I too use air conditioner but it still doesn't helps me

That freezes me and worries me like hell xD

I don't wish to listen to songs as it drives my concentration... + beware of bacteria's on your mouse

If bacteria is a problem, why do you use your hands?

We can wash our hands properly.

Different things work for different people. Try checking if you blunder against higher-rated opponents or against guys weaker than you are. It might help to understand if the root cause if fear or nonchalance. If, as you said, you are afraid of blundering, then it might help to do a blunder check. Look at the position after discarding your previous thoughts about your chosen move; this helps (at least, it helps me!) to cut down on blunders. However, blitz and bullet games allow no time for second-guessing yourself, so you got to be careful.

Same for nose