When you send your girl a dick pic, but she says it's small, so you text back and say:
"Enjoy the little things."
Listen up, buttercup. The joke is about a dude who ain't packin' much downstairs. His girl calls him out on it, so he tries to play it off by saying, "Enjoy the little things." It's funny because he's making a joke about his own inadequacy, and you are dumb for not getting it.