How quickly we forget that God's grace is far greater toward us through righteousness in Jesus Christ! (Romans 5:20-21). Think about that for a minute.
The person that remains under the judgment of God for their sin and who will justly deserve it too, if they are coming to God with humility of heart before the Lord, the blurriness of God's grace begins to become more clear and the joy of forgiveness and salvation in Christ more exciting than ever before.
When Peter witnessed the tremendous catch of fish with Jesus on his boat, he felt deeply convicted in his heart to say to Jesus, “Depart from me, for I am a sinful man, O Lord!” (Luke 5:8).
Can we say like Peter did that Christ is not for me, depart from me because I am a sinner?
We can relate to Peter's assessment of himself before the Lord, at least those who are honest about it. But Peter didn't depart from the Lord despite the tremendous catch of fish, he followed the Lord. He did deny Jesus before He was crucified, but again, in God's mercy and grace, Peter was restored and instructed by Jesus to care for those that would follow the Lord after His ascension (John 21).
Matthew Henry's Commentary says concerning this passage (Luke 5:8), "Those whom Christ designs to admit to the most intimate acquaintance with him he first makes sensible that they deserve to be set at the greatest distance from him. We must all own ourselves sinful men, and that therefore Jesus Christ might justly depart from us; but we must therefore fall down at his knees, to pray him that he would not depart; for woe unto us if he leave us, if the Saviour depart from the sinful man."
We are all like Peter, sinful and unworthy of to be in the presence of Christ. But God is so rich in His mercy and grace, that only by the blood of His Son are we able to enter into His presence with joy and not fear.
The following quote is by Martin Luther, which I read in Alister McGrath's book, Theology The Basics. What Martin Luther said is quite indicative of the doubt people feel that they are unworthy of Christ and God's forgiveness, but they are!
I have often spoken about two different kinds of faith. The first of them is like this: you believe that it is true that Christ is the person who is described and proclaimed in the gospels, but you do not believe that he is such a person for you. You doubt if you can receive that from him, and you think: "Yes, I'm sure he is that person for someone else (like Peter and Paul, and for religious and holy people). But is he that person for me? Can I confidently expect to receive everything from him that the saints expect?" You see, this faith is nothing. It receives nothing of Christ, and tastes nothing of him either. It cannot feel joy, nor love of him or for him. This is a faith related to Christ, but not a faith in Christ...The only faith which deserves to be called Christian is this: you beleive unreservedly that it is not only for Peter and the saints that Christ is such a person, but also for yourself - in fact, for you more than anyone else. Martin Luther.More than anyone else.
"Let the redeemed of the LORD say so, whom He has redeemed from the hand of the enemy," Psalm 107:2.
McGrath, Alister E., Theology The Basics. Oxford: Blackwell, 2008.