Yup, My son knows what ya mean- he started working graveyard shift at McDonalds last week- been lifting weights for football all month- isn't used to sleeping days so I got a call from coach that he had passed out when he was feeling bad on the field after they ran a dash in competition (just low blood sugar-gatorade works wonders then- he had worked the shift right before but had camped out with buddies the night before (i.e. no sleep). He's fine but slept like the dead yesterday afterwards.
Besides ya need your beauty rest for certain!