What is the difference between "earn" and "fulfill"?
It makes me feel I earned it. [You worked hard to obtain it, and you get it as a fair reward for your efforts; you deserve it after your dedication.]
It makes me feel I am fulfilled by that. [Whether you deserve it or not is not an issue in this sentence; you feel satisfied, happy or elated because what you obtained gives you more than just pleasure, it is a step towards your personal growth.]