There is a Dunning-Kruger-esque quote on painting, that applies maybe even better (*) to software:

"Painting is easy when you don't know how, but very difficult when you do." (E. Degas)

(or for a more literal translation: "Painting, that's very easy when you don't know how to do. When you do know, it's very difficult.")

(*) (Although Ecce Homo by E. G. Martinez is a good image of what can happen to the software you're working on when management adds someone to help you out ;).