Fun is overated. Being a great bass player requires you to get off on making other people sound good. Once you get that and make it so, its the best fun in teh world. But getting to that space is not all 'fun'; it can be damned hard work. Satisfying? Rewarding? Yes, but fun? Not always. But what I will say is that, particularly in the early stages, it is when it is NOT fun that most of the learning is taking place.