I go through a stage every few months where I wonder if I should quit. Usual reasons - slow progress, had a bad session, always working on the same old stuff. But then I have a lesson that I really enjoy and forget about quitting. If I really hated it, I would walk away, but that's never really the problem.
(For the record, I can't spin at all, not even a two foot spin. Gave up trying ages ago, but it wasn't a major goal of mine either, so it doesn't actually both me)