A case of the black ass - You're so exhausted your butt looks like it was dipped in a

You're so exhausted your butt looks like it was dipped in a coal pile and ran over by a truck.

I had the black ass after that marathon and my pants were soaked.

My dog gave me the black ass after I forgot to feed him.

I got the black ass so bad I fell asleep in the middle of the street.