The Art of the Novel #3 : The Art of Love

It's been weeks and I still haven't gotten over the little sentence tucked away in the middle of Updike's essay in the New Yorker on the late works of great authors. I include it here with the preceding two sentences as context:

Hawthorne's inability to carry forward and complete, "The Ancestral Footprint" was, in Adorno's term, a "catastrophe" for him personally. His struggles to find the key—the handle—demonstrate what a precarious feat it is to write a novel, organizing a host of inventions and polished details into a single movement toward resolution. Like sex, it is either easy or impossible...

Does this simile hold up? Am I screwing the wrong book?