My heart pounds

I just told a man that to panic in an situation where everything has gone wrong can only be detrimental, so why do I panic when the sale is slipping away? It's already gone, being nervous about it won't bring it back. Do your job, let it go, keep moving. Don't care. How can I control the pounding? How can I stop it? It doesn't pound when everything is going smoothly, so the solution is to make everything work, by not caring. How to not care? Keep going.