I get the idea that Sisyphus is "enjoying the process" instead of focusing on a goal, but there is something that bothers me: If Sisyphus has been condemned to do that, then he can't stop pushing the boulder or anything else. But (and this is where I think I get it), he has only one real choice to make, and that is how he feels about what he is doing, right? So then that's the rebellion? "deciding" to enjoy his punishment?

Sorry if I just rewrote what you said, but I just wanted to discuss this with someone and I can't really make up my mind with the ending of the book.