Discipline prepares us to shift paradigms.
Improvement comes when we move from our present state to the next level with fresh inputs and new realities. This is broadly known as "elevation in paradigms."
Paradigms are ordinarily a multitude of habits of any individual. Habits are formed or transformed when something is done consistently, keeping discipline at the core. Now look at related dimensions. 
First, leveraging our experiences to meet the new conditioning or keeping pace with shifting circumstances adds to our perspectives. Here we are observing the whole state of affairs from a fixed angle. We need to rotate this angle to the next.
Second, reading a variety of books is not sufficient to equip us with the skills to handle family affairs, relationship issues, evolve empathy, and win trust. We need more life skills. 
Third, our past performance attests that we are capable of doing more. We need to get ourselves ready to adopt new paradigms. 
Fourth, the math of life is not like the numerical problems we solve by applying formulas. Every time, we set our own new formulas to get the personal, professional, or social issues resolved. 
Some dimensions are described above, not to discourage but to make us aware of the diversity of tasks ahead. 
Self-discipline is the best tool to add new habits and delete bad ones so we can achieve more in a short period of time.
Like other virtues, discipline also evolves. We must focus our attention across our range of disciplines. We are good at hedging but bad at keeping our schedule intact. We have to be sufficiently disciplined as individuals. 
Discipline makes all our tasks achievable. Know that discipline is the pivot for all other virtues.