Grace
Is simply "unmerited favor." You can show grace to others when you are kind in the face of someone's abuse of you. That is grace. Such a person has not earned your kindness, yet they will often be moved by it because it so rare. God is the Author of this.
God's Grace is perfect, of course. He showed the ultimate Grace when He paid the price for our sins on the Cross. When we accept that Sacrifice as the payment for our sins, we are Saved from our sin and become "justified to God" by Grace (as opposed to by works). At that point, all of our sins - past, present, AND FUTURE sins - are all forgiven. That is Grace. We will continue to feel that we have let God down enough through or future sins that we need to atone for them somehow. But that's not the way God looks at it. Our human nature makes us feel that we must DO something to atone for those sins (that's the counterfeit of religion) - even after we are Saved. But in truth, your repentance is enough.
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