The essential idea of tahzeebe akhlaq is to bring our natural faculties in a state of balance. The three basic faculties are anger, desires, and intelligence.
When in equilibrium it results in valor, forbearance, steadfastness, the ability to restrain anger, and dignity. Excess will result in rashness, boastfulness, pride, inability to restrain anger, and vanity. A deficiency will result in cowardice, disgrace, and feeling of inferiority.
Equilibrium here results in chastity, generosity, haya (decency), patience, and contentment. Its excess leads to greed and lust. The other extreme results in narrow-mindedness, and impotence, etc.
Equilibrium here makes man wise, sharp-witted and one with great insights. Excess here makes one deceptive, fraudulent and imposture. Its lack results in ignorance and stupidity with the consequence that such a person is quickly misled.
A person will be considered as having a beautiful seerah (character) only when these faculties are in the state of balance and equilibrium. Internal beauty varies with people just as external beauty does. The possessor of the most beautiful seerah was Prophet Muhammad, Sall-Allahu alayhi wa sallam. The beauty of our seerah is based on its closeness to his seerah.
[Condensed from writings of Maulana Ashraf Ali Thanvi]
Note: Extracted from Khalid Baig's "What is Tasawwuf?"