In the Book of Psalms, King David teaches that, "The beginning of wisdom is the fear of God." From this verse–as well as other sayings of the sages such as "where there is no wisdom there is no fear"–an equation is made between chochmah ("wisdom") and yirah ("fear of heaven"). The Talmud goes even further and teaches that, "Three things are equivalent, each with the other: fear of heaven, wisdom, and humility." The Talmudic commentators known as the Tosephot explain this to mean that a person cannot attain one without the others–not fear of heaven without chochmah, not chochmah without fear of heaven, and neither of them without humility.
This means that when we fear heaven, we cultivate chochmah (that is, koach mah which is selflessness). Self-gratification and self-praise are the most subtle roots of sin. Chochmah, on the other hand, requires humility, which is only possible with self-criticism; when we regularly reflect upon our behavior with a critical eye, we guard against lapsing into complacency and self-justifications.
The ultimate realization of the above is in the fulfillment of the saying of the sages, "Give to Him what is His, for you and all that is yours are ultimately His." As King David also states, "For all things come from You, and of Yours we have given back to you." This is ultimate selflessness, when we recognize that God is the means and the end–He is all, and we are naught.
In summary, self-criticism, as prescribed above, is not an end in itself, but a means toward serving others. Its purpose is to dissolve the ego rather than strengthen it, to create givers rather than takers. But self-exploration for its own sake can degenerate into self-indulgence, fostering self-centeredness rather than selflessness. Self-reflection is only productive in proportion to our ability to conquer our ego. Those who push beyond their capacity of selflessness will end up magnifying their neurotic tendencies rather than eliminating them. This is a delicate and dangerous balance.
Honest self-reflection deepens our capacity for empathy. As we become more aware of our own inclinations toward selfishness and self-rationalization, we regret this, and struggle with it, discovering ways of overcoming it so that we can share with others. Then we become a "fellow traveler" and not a finger-pointing accuser. Words which come from such a place of humility are softened with compassion rather than sharpened with judgment, and for this reason they penetrate into the heart of the receiver and influence him or her positively and productively.