Speaking about his new movie, Attack of the Clones, Star Wars creator George Lucas described how the young Anakin Skywalker became the evil Darth Vader:

He turns into Darth Vader because he gets attached to things. He can't let go of his mother; he can't let go of his girlfriend. He can't let go of things. It makes you greedy. And when you're greedy, you are on the path to the dark side, because you fear you're going to lose things, that you're not going to have the power you need.