The main subject (of taking the Precepts and the Bodhisattva Vow) is how to become a transmitter of actual light - life light. Practice takes place to shape your whole ability to reflect the light coming through you, and to generate - to regenerate - your system, so the light increases its power. Each precept is a remark about hard climbing, maybe climbing down. You don't use the precepts for accomplishing your own personality, or fulfilling your dream of your highest image. You don't use the precepts in that way. The precepts are the reflected light-world of one precept, which is Buddha's mind itself, which is the presence of Buddha. Zazen is the first formulation of the accomplishment of Buddha existing.
The more you sense the rareness and value of your own life, the more you realize that how you use it, how you manifest it, is all your responsibility. We face such a big task, so naturally a person sits down for a while. It's not an intended action, it is a natural action.