The heart is the core of our personhood, and the source of behaviour causality. What a person says or does is shaped by the thoughts and desires of the heart (see Luke 6:43-45). Heart change is always the result of the grace of God. You and I simply have no ability whatsoever to change the heart of another human being. We are never anything more than the tools of change in the hands of a powerful, wise, loving Redeemer. When we attempt to do God’s job and change someone’s heart, we only cause frustration to ourselves and pain to the other person.
At another level, often our efforts to change another person are nit only futile, but completely mistaken. Sometimes, there is actually nothing wrong with the behaviour that bothers us. The person is simply different than we are, which means the problem is in us.
-Paul Tripp, p.65, Broken Down House