Any sort of surgery is just hell on the body.
It throws a lot of your biochemistry out of whack. Your body spends a lot of time pumping you full of endorphins and other hormones, in an attempt to alleviate pain. Its a lot of hormonal up and down, following any invasive surgery.
Take care of yourself, stay well-hydrated, eat plenty of healthy foods, and stay active within the limitations of your surgeon's recommendations.