Please read this Bible passage and think about what it shows about how people change:
But if a wicked person turns away from all his sins that he has committed
and keeps all my statutes and does what is just and right,
he shall surely live; he shall not die.
of the transgressions that he has committed
shall be remembered against
for the righteousness that he has done he shall live.
Have I any pleasure in the death of the wicked, declares the Lord God,
and not rather that he should turn from his way and live?
But when a righteous
person turns away from his righteousness
and does injustice and does the
that the wicked person does, shall he live?
None of the righteous deeds that he has done shall be remembered;
for the treachery of which he is guilty and the sin he has committed,
for them he shall die.
~Ezekiel 18:21-24, ESV
A wicked person can turn away from his sin and become obedient to God, and live.
A righteous person can turn away from his righteousness and do the same things that a wicked person does, and die.
There are three things we need to learn from this:
(1) We should not categorize people as righteous or wicked.
Perhaps this is part of what the Lord means when He admonishes us not to judge. We know neither the backstory, nor the end of the story. Only God knows everything, past, present and future.
We should be discerning about people based on what we observe in the way they live each day. People are not our example; Christ is our example, and scripture is our standard. If people live in obedience to scripture and walk in the footsteps of Christ, we can let them be an example to us for as long as they walk well. A tree is known by its fruit, and a man is known by his walk.
Never just set up a man as "my righteous example," and then follow him blindly. No man is Christ, and no man ever will be. Rejoice when a man walks well, grieve when he stumbles, and always evaluate everything under the light of the Word of God.
(2) Be ready to forgive a sinner who repents.
Just as we need to avoid categorizing someone as a righteous, infallible example, we also need to avoid categorizing someone as a bad person.
People make mistakes. We all do. I surely do, and I'm willing to bet a million dollars (which I don't have) that you do, too. Some people let us down or disappoint us more often than others, but always remember that God is at work, and everyone has equal access to grace. You never know when someone might avail himself of grace.
Children who hate vegetables can grow up to be adults who love salads. And sinners can turn to Christ and be changed.
We must never withhold forgiveness from someone because we decided twenty years ago that he was not a nice person. (We must never withhold forgiveness anyway, but this is a particularly bad reason.) God always forgives, and He tells us to, too. Yes, we need to forgive the person who used to be a complete jerk.
(3) The only way to be sure of our own salvation is to abide in Christ who is our righteousness.
We are helpless to be consistently righteous on our own. A person without Christ may do a kind or generous thing now and then, but consistent righteousness cannot happen apart from Christ. At best, without Christ, a person can do lots of righteous things and be motivated to continue because of pride in himself. The pride undoes all the benefits.
Christ has come to impute His righteousness to us, to wash us from our sins and cleanse us from all unrighteousness. He bore our sins so we could be clothed in His righteousness. There is no other way we could be pure enough to enter into fellowship with God, but because of Jesus we can. Because of Jesus, the very Holy Spirit of God comes to abide in our hearts and direct our desires and bear His fruit in our lives. God does it all, and yet there is a need for us to actively respond to His work in us, to cooperate with Him and seek His face. This is a great mystery, the mystery of faith which comes from God, draws us to God, and sustains us in God.
To abide in Christ is
to live in the protection of His love,
to have confidence in His perfect faithfulness,
to soak my mind in His Word and my soul in His Spirit,
to pray without ceasing,
to seek His beauty and apprehend His worth,
to turn my desires over to Him and rest in the goodness of who He is,
to allow Him to propagate peace, joy and obedience in all my days.
This is the only way to consistently change in a good and positive way. Abide in Christ.