The Kabbalist Rabbi Yaakov Meir Shpielman (1813-1888) explained that in Judaism "spiritual growth" means downloading the lights of one's own soul. The more one works on refining one's own mind, heart and body, the more they become receptacles for the lights of his/her soul. As a result, the person spiritually grows.
It occurred to me that perhaps this is one reason why the soul is so multi-leveled or layered. This way the growth is not designed to be a potentially discouraging "all or nothing" process. Rather it's designed to be gradual, allowing one to taste the growth as it occurs, level by level, in real time. By tasting the growth along the way, one can then more easily find encouragement to continue onward - as a sense of that it's "really happening" is ever present with every step.