The core of the Force–you got the Dark side and the Light side. One is selfless, one is selfish. And you want to keep them in balance. What happens when you go to the Dark side is that it goes out of balance, and you get really selfish and you forget about everybody. And you ultimately lead yourself because when you get selfish, you get stuff, or you want stuff. And when you want stuff and you get stuff, you get afraid that someone is going to take it away from you, whether it’s a person or a thing or a particular pleasure, experience. And once you become afraid that someone’s gonna take it away from you, or you’re gonna lose it, then you start to become angry, especially if you’re losing it. And that anger leads to hate, and hate leads to suffering, mostly on the part of the person who’s selfish. Because you spend all of your time being afraid of losing everything you got, instead of actually living…

…where joy, by giving to other people, you can’t think of yourself, and therefore there’s no pain.

–George Lucas