I've written a number of books, and I've never suffered from writer's block - thank God.
But I don't know if I would subscribe to Tom Clancy's notion, in Can You Ever Forgive Me? (2018), that writer's block is synonymous with laziness (i.e., the antithesis of grit).
Tom Clancy: "I don't subscribe to the notion of writer's block."
Female Admirer: "You never experience it?"
Tom Clancy: "Writer's block is a term invented by the writing community to justify their laziness. My success is nothing more than that I have the determination and stamina [i.e., grit] to sit and get the work done."