Calling again on the insight of M. Scott Peck, who listed balance among the four tenets of discipline, I am grateful for his elucidation and expansion on this distinctly essential virtue.
Balance is a thing to which I feel particularly sensitive. What is required to achieve it is different for each person, and its perceived importance varies as well. For me, it is crucial; I know that I like an eclectic array of interests to be served in my life, and that moderation is a great equalizer.
In general, balance requires strength, determination, discipline, and ultimately flexibility. Balance means maintaining a sense of evenness, but it also involves a capacity for adaptation to achieve such maintenance in a changing world. In order to stand on one foot on a hill in the wind, you have to be able to constantly make minor adjustments as the forces change. Similarly, in order to preserve balance between opposing forces in your life, you must support an equilibrium; it's not balance if you favor one extreme or the other; you have to accommodate each of them to a degree that zeros your scale, so to speak.
May you find peace and harmony :)