1 Then you will say on that day, “I will give thanks to You, O Lord; for although You were angry with me, your anger is turned away, and You comfort me. 2 “Behold, God is my salvation, I will trust and not be afraid; for the Lord God is my strength and song, and He has become my salvation.” — Isaiah 12:1-2 (NASB)
Living a Holy life is impossible on a human level. Just as the people in the Old Testament could not fulfill every point of the law, we cannot live a sinless life. Jesus was and is the only perfect man. There will be times that we fail (and sometimes we will fail miserably) but Jesus has already paid the price for our forgiveness. So, if you have sinned (intentionally or unintentionally), you are already forgiven. Do we need to confess those sins? Yes, forgiveness is free, but you have to ask for it. When Jesus was hanging on the cross and He said, “It is finished”. All of His redemptive work for all times was complete. Jesus is not going to die on the cross again. So, if satan is beating you up over a mistake you made, quote him a Word of Scripture and/or sing Him a good old hymn. Just tell him, “God is my salvation, He is my strength and my song. The point is this, we cannot live perfect lives, but God forgives and restores. Don’t let satan trick you into thinking that now you are useless to God. Nothing could be further from the truth. God still has a plan and a purpose for each of us. God sees each of us as a finished project while we can only see the work in progress. Just remember, it is impossible to surprise God. Before He saved us, He already knew the mistakes we would make, but He saved us anyway. So rejoice and sing praises to Him because He is always faithful.