I sometimes find that playing the bad guy, or villains, or psychopaths tend to be much more psychologically rewarding. And you can really push it, you can push the limits, and get away with it. ↗
Let's face it; by and large math is not easy, but that's what makes it so rewarding when you conquer a problem, and reach new heights of understanding. ↗
I love scoring. Putting music to picture is a rewarding challenge and one that relies on interpretation of emotion - as in, what is the pivotal feeling in a scene and which character's point of view is driving it at any given moment? ↗
And the fact that you must make the movie for yourself because no one else will ever fully appreciate the endeavor, makes it a more rewarding challenge. ↗
I don't hate work, composing is not work for me, it's my pleasure; it's my life. So why should I stop? If something is pleasurable and exciting and rewarding, why should one stop? ↗