Trust can be as strong as iron, yet fragile as a flower. Many times when trust is broken, our capacity to confide in that person falls to zero. Either it's complete trust, or complete distrust.
But we can't write people off in a moment's time. Those who have wronged you must be allowed to earn back your trust. Forgiveness and redemption must be a part of our language. If we only trusted those who have done no wrong, we would find ourselves alone very quickly.