Self-discipline is the ability to control one's thoughts, actions, and feelings to accomplish goals even when faced with temptations or challenges. It is built through practices like accepting reality, using willpower to overcome laziness and negative habits, working hard consistently through both easy and difficult tasks, being industrious with one's time, and persisting in continued action even when motivation wavers. Developing self-discipline can help people achieve long-term goals by resisting immediate desires and making choices that provide future benefits in addition to present rewards.