Our God is a God of both grace and mercy. In the English language, grace is generally unearned, unmerited favor. Mercy is demerited favor that we receive anyway. When we have forfeited goodness, and God gives it to us anyway, He is showing mercy.
When Adam was first created, he had obviously done nothing to deserve it, so his experience of the Garden before the fall was an experience of God’s grace. After he fell, and God promised a savior, this was mercy. Adam had forfeited God’s kindness, and yet God remained kind to him anyway. All mercy is obviously grace, but not all grace is mercy.
But the reason for mentioning this is that we are called as Christians to imitate God in both His grace and mercy. When you bring a baby home from the hospital, you spend a lot of time delighting in him, long before he begins pulling his weight. That is grace. But when someone has wronged you, and asks forgiveness, or worse, has wronged you and has not asked forgiveness but needs your help with something, to extend that help is mercy.
And we are to be merciful, just as our Father in heaven is merciful. We don’t want to extend mercy because it was demerited, but that is the only way we can extend it. We don’t want to extend forgiveness because the person doesn’t deserve it—I mean, look what he did. But genuine wrong-doing is a precondition for forgiveness. When you bump into someone accidentally, you should say, “Pardon me.” When you knock him down on purpose, you should say, “Forgive me.” But we don’t want to forgive, because forgiveness is the only thing that is really called for.