We who have received His mercy, yet we have no mercy for others sins. For if you forgive men for their transgressions, your heavenly Father will also forgive you. But if you do not forgive men, then your Father will not forgive your transgressions. Making things right is important for Christians. Whether it be a relationship, a debt or something you took that was not yours.
Restitution is necessary in order to receive forgiveness.
One can apologize and ask for forgiveness but, most important is changing the behavior. Sometimes we take the attitude of let bygones be bygones or let our own pride take control. We rationalize that it is past and why drag it up and start trouble again, yet we not only damage others, but ourselves as well. And this is certainly not a Christian attitude. The world is constantly watching us to see how we react to others.