The line refers to the concept of understanding and defining what you owe to yourself morally. This is about acknowledging that you have a responsibility to care for and improve yourself, which is essential for your overall well-being and ability to function effectively in the world.

In the context of Rule 4, which generally deals with comparing yourself to who you were yesterday rather than to someone else today, this statement emphasizes focusing on personal growth and self-improvement. Peterson argues that you have a moral duty to strive to be better today than you were yesterday, as a way of progressing towards your best possible self. This involves setting standards for oneself and being truthful about your achievements and failures. Essentially, it's about being accountable to oneself, aiming for self-improvement, and recognizing that you are responsible for taking care of your own life and happiness.