Try focused breathing techniques like musicians. Breathe in through your nose, out through your mouth. Slowly. Exhaling fully. You need to fill your diaphragm, your stomach extends.
try to meditate for a few minutes[ quiet the body quiet the mind]
I wish I could give you a solution, I too do this it can last a whole day! But the only thing that helps me is doing something else like going for a walk etc , some days it helps and some days as soon as I'm back home I focus on breathing again, I find sometimes lying down watching tv helps