When someone cheats or insults me, my instinct is to answer harshly and get even. Does good character mean I just let people walk over me?
The fire you feel when someone wrongs you is not a flaw in you. It is a sense of honour, and honour is a good thing to have. The only question is what you do with it.
You ask whether good character means letting people walk over you. It does not. There is a difference between weakness and restraint. Weakness is when a man cannot answer. Restraint is when he could answer with full force and keeps that force in his hand, the way a rider holds the reins. The Prophet, peace be upon him, drew exactly this distinction.
“The strong man is not the one who overpowers others in wrestling; the strong man is the one who controls himself at the time of anger.”
The Prophet (peace be upon him), Sahih al-Bukhari (6114) · meaning
Read it closely. The one who lashes out is not the strong one. He is being pulled along by his anger. The strong one stays seated, master of his own heart. When you swallow the harsh reply you have not lost the argument; you have won a larger one, inside your own chest.
And the Qur’an asks for more than merely holding back.
“Repel evil with that which is better, and behold, the one between you and whom there was enmity will become as though he were a devoted friend.”
Qur’an, Fussilat 41:34 · meaning
Answering harshness with harshness only doubles it, and you become a second copy of the thing that hurt you. Answering with something better, a calm word, a dignified silence, an unexpected kindness, can end the enmity altogether. We notice this in ourselves too. A composed answer, neither doormat nor fighter, often cools a quarrel where a sharp one would have fed it, and it leaves our dignity standing exactly where it was.
Allah names this quality among the qualities of the people He loves.
“Those who restrain their anger and pardon people; and Allah loves the doers of good.”
Qur’an, Aal-e-Imran 3:134 · meaning
So you are not asked to be walked over. Protect what is yours, speak up where speaking up is needed, but let the answer come from your dignity and not from your temper. That is the harder road, and the higher one, and with Allah’s help it turns into a habit.
One small step: The next time a sharp reply rises in you, take three slow breaths before you say anything, and in that small silence ask Allah to make your answer the better one.