In life, I am convinced this is both the hardest and most important lesson to learn. It has nothing to do with not fighting for something "greater" and "different" from what you have, and it's so much bigger than being happy wherever you are. No man, on our earth, can master it, for it is a lesson that must be learned every day of our lives. Being content doesn't hinder or change our aspirations; on the contrary, it allows us to pursue what we want in a better, more prioritised way.
Contentment means, in the end, that God is put first, because once we stop wanting our own agenda and are ready to accept God's, then we are happy in the world he put us, and more importantly, under the circumstances he has set for us. Balance your own desire to be more, for whatever good reason you may have, with the truth that God has you where you are for a reason: maybe it's to learn something, maybe it's to teach you as simple a thing as patience, before you can continue on your journey. More, it's not so much spending all your time wondering, "What lesson can I possibly be meant to learn and how can I learn it so this will be over?" Rather, ask what you love best, and root out the selfishness found in your own being.