A Devotional Verse From The First Letter Of John, The Apostle
I write unto you, little children, because your sins are forgiven you for his name's sake.
1 John 2:12
     This verse clearly answers the question "When a Christian sins why can they be forgiven?" Look at the scripture verse: We are not forgiven because we've been good. We are not forgiven because we are Christians. We are not forgiven because God owes it to us. We are not forgiven because we had a good roll of the lucky dice. We are forgiven for his name's sake.
     Earlier in the chapter we are told that He, Jesus Christ, is our advocate with the Father (2:1). An advocate speaks up for another. Then we are told that Jesus is our propitiation (atoning sacrifice NIV 2:2). This is why we are forgiven for his name's sake. Because of Jesus God forgives the sinning Christian, but, of course, the back story is found in verse two also because we are told that He is the propitiation for the sins of the whole world, so that we understand we are forgiven of our sins and saved for his name's sake which makes us into Christians, and then when we confess our sins while living the Christian life we are forgiven them daily for his name's sake.
     This, to the Bible believing Christian, is a very simple concept, and yet it is so hard for people who do not know what God says in the Bible to understand, because they feel they have to do something to be forgiven, or they want to do something to know that they are worthy of being forgiven. According to God's word it is not possible for us to be worthy of forgiveness or do anything that would require God to give us forgiveness. If you want to get forgiveness, and you, or anyone, can have it if you want it, then Believe on the Lord Jesus Christ, and thou shalt be saved,... (Acts 16:31) ...because your sins are forgiven you for his name's sake.