"It is not the accumulation of extraneous knowledge, but the realization of the self within that constitutes true progress." - Okakura Kakuzo on Judo In The Empire Strikes Back, Luke is sent into the Dark Side Cave by Yoda. Yoda says, "That place… is strong with the dark side of the Force. A domain of evil it is. In you must go. What's in there? Only what you take with you." In the cave Luke is confronted by Vader and he strikes him down, but as Vader's helmet falls to the ground it is Luke's face that appears in it. In the DVD commentary, George Lucas stated that, "Had Luke gone into the cave with no weapons, he would not have met Vader in there. It was a way to teach the person, by showing them what the Dark Side can bring from inside them. Yoda said that what is in there is "only what you take with you" - Luke takes his weapons, he's aggressive - he's making the same mistakes Anakin did 25 years before, and could end up the same way. Note that it is Luke who activates his lightsaber first, not Vader - Luke is the aggressor."
The one thing in life we have control over is choice. Every moment we get to choose who and what we want to be. In every person's life some rain must fall, but that doesn't make it who you are. Everything that happens to us in life "makes us" who we are but we get to choose how based on our perspective. Good, bad, right or wrong are all relative to how you choose to see the world. As a martial artist, we choose to see everything as an opportunity to improve and thus something that will makes us better. What path will you choose?