The hot shower at the end of a cold run. The big meal at the end of a hard training session. The paycheque after writing an article people enjoy. The view at the top of the mountain after hiking up it.
But the best?
The best reward?
The best reward is the one where you get to keep doing the thing you enjoy doing.
For the writer, it's being able to write every day.
For the programmer, it's being able to code every day.
For the painter, it's being able to paint every day.
For the martial artist, it's being able to practice every day.
Deep down we're all artists. And any real artist will tell you the best reward is forgetting where they are. Getting lost in the work. Letting it happen. All the others are short-term.
When you're in the flow when your soul is singing when the work is creating itself, that's the best reward. It's the runners high, it's when the blank page fills itself, it's when the records get broken and the person gets asked how'd you do that and they reply I don't know.
The thing both of these kinds of rewards have in common, the small and the large, the short-term and the long-term, is getting started.
Whatever reward you're seeking, the nice dinner after a workout or getting to work on your craft every day. It's there if you want it.