Belle is an influential proponent of discipline and control in parkour, saying, "Precision is all about being measured," and going on to describe parkour as an art that requires huge amounts of repetition and practice to master. "With parkour, I often say, 'Once is never'. In other words, someone can manage a jump one time but it does not mean anything. It can be luck or chance. When you make a jump, you have to do it at least three times to be sure you can actually do it. It's an unavoidable rule. Do it the hard way and stop lying to yourself. When you come for training, you have to train. Even if it means doing the same jump fifty or a hundred times." To its founder, parkour is a method of self-refinement, used for learning to control and focus oneself.