In Hebrew good attributes are called “good measures,” which suggests that the excellence of a quality is determined by its proportion, not by its being what it is in itself, but by its properly related use in particular circumstances.
Everything that is not in the right measure, that relates out of proportion to a situation, tends to be bad.
The good is thus that which is contained within proper limits, and the bad, that which breaks out and goes beyond these limits.
And it does not matter whether this exceeding of boundaries is positive or negative, restrictive or excessive, whether refusal of affection or even generosity in love.
And, in fact, this need for balance is true of every living organism.
Each cell in the organism has a certain form and a fixed rate of growth.
And whenever its form is distorted or its growth exceeds what it should be, the result is pathology.
The evil in the world is just such a bursting of bounds, that which allows for the existence of parasitic and injurious factors.
–Rabbi Adin Steinsaltz