I am guilty of being very tense at times - even to the point that it could be detrimental to my own health ;p
I guess it has partly to do with my personality - rather high strung at times. So what I do - serach sites on how to relax. One of the recoomendations is to take a calming walk...and another would be to just leave things later. I remember one of my friends used to say : Work can wait - it sounded funny when she said it but I suppose she has a point.