When your child pees on you, you have to be able to laugh.
When your child vomits in your mouth, you really have to be able to laugh after you gag.
When you change your newborn's diaper and they immediately poop, you have to laugh, and then you have to laugh harder when they do it again. Forty-three seconds later.
You have to laugh because if you don't, you'll cry buckets. And really, it is all pretty comical. Living with a newborn is a bit like living in a sitcom...without makeup and wardrobe and craft service.
For the record, your sense of humor will carry you nicely through the toddler/preschool years, too. Trust me, if I didn't laugh regularly at S, I'd have to lock her in a dungeon.