Why is taking a break so hard?

IUI#1 just failed, we have male factor infertility. We are taking a two month break off so the hubby can see an infertility urologist and so we can "de-stress" a little. I know this is a good thing, TTC has literally taken over our lives and relationship, and the stress has caused me to gain a wonderful 15lbs. But why is it so hard to let go for awhile? How am I not supposed to think about it?