Good Art Has No Excuses
A saying which states that one artist (a writer, painter, author, musician, etc.) should be allowed to only make art for himself and not for random people he doesn't know, but should keep in mind that it should not excuse him from making poor quality art.
As a writer, I only write for myself and not random strangers who read my novels, but that doesn't excuse me from writing good quality books. Every artist should know that good art has no excuses. Ever.