Physical improvement, mental improvement, these are essential, but also essential is dispositional improvement.
Spiritual traditions and religions have all kinds of words for it, and I don't care for them. I am partial to the term "Resolve", though more classical terms like "will", "heart", "spirit", "soul", or whatever also represent the same faculty.
Resolve is a force of differentiation, and can be seen to operate in the face of chaos. It often involves the recognition of many potential and the refusal of certain potentials in favor of others. It is the essence of a human's ability to navigate quantum potential.
Unfortunately, the only way to effectively train and develop the resolve that I know of is trial by fire.