Productive work, in general, is fulfilling even if you don't happen to like your current "job." It is not the job itself, it is the act of taking action in order to achieve your values. If you value producing art, that is productive work even if it's not your "job" and even if it doesn't pay the bills. You are achieving some value from that. If you are truly fortunate you can find a way to monetize doing work that you would do even if it didn't pay ... but if your job is "just a means to an end", that end is clearly a value and the job is helping you achieve it. It's the achievement of the value that is rewarding.