Learn to want exactly what you have.

I read a story, a parable once, and I'm going to relay it to you.

I was walking past a homeless man one day, who had nothing to his name save for the clothes on his back and the cane in his hand.
I stood in front of him, he was sitting on the ground, and I asked him, "How can I help you? Is there anything I can do for you?"
"Yes," he said. "You can move, please. You're blocking the sun."

Learn to want exactly what you have, and you will never be unhappy.