You certainly can find productive tasks enjoyable, but it's common to find productive tasks unenjoyable. People don't hang out with each other because it's productive (except when networking), they hang out because it's fun. The fact that it's good for your health is a bonus, but isn't and shouldn't be the primary motivation.
Having fun is certainly something that you can do, but that doesn't mean that it is obviously morally optimal.
Not obviously morally optimal, but it is actually morally optimal, for a broad enough sense of "having fun". But I say this as an ethical egoist.
but it is actually morally optimal, for a broad enough sense of "having fun". But I say this as an ethical egoist.
Just because you are an ethical egoist does not mean that ethical egoism is the system by which all moral claims ought to be judged. Have you read the metaethics sequence?
If it's worth saying but not worth its own thread even in discussion it goes here.