Self discipline is the tool to pull us out of the rut of self-centeredness. Self discipline is not about having good personal hygiene, being punctual, obedient, or tough. Self discipline has nothing to do with keeping your word, being consistent, or exercising.
Self discipline is looking out at the world and saying, "I’m not going to be petty. I’m not going to retaliate. No matter how many people are being that way, I'm not going to let myself become that." You will always feel these emotions, but with vigilance and discipline you can keep from acting on them.