My definition of work - life balance
Work - life balance is, in fact, the ability to manage our time, effort and attention in a way that allows us to meet our needs the best way possible. Our work satisfies our needs, including financial security, significance and contribution, and the “life” aspect satisfies our needs for love, fun and personal growth, among others.
To “have work - life balance” then, means that one has designed life (as a whole, not in contrast to work) in such a way, that all the needs can be met to a desired, or at least satisfactory degree. An individual can be successful in one area (financial, for instance) but not others, which indicates lack of balance and is caused by neglecting the unmet needs in favor of the primary need that gets most of the time and attention.