I am of the belief that believers should walk by faith and claim the victories that come with salvation. Therefore it seems to me that since all our sins are forgiven because of the sacrifice that Jesus paid on the cross we should do as scripture say, 1John1:9 if we confess our sins He is faithful and just to forgive us our sin and cleanse us from all unrighteousness, there I would say to confess the known sin and thank Him for paying your sin debt, that way you walk by faith trusting that He did as He said He would do, never to remember them no more. Look at David's sin when he was confronted by Nathan, you can read the whole context in 2 Sam 12, but I will show this v13-14 So David said to Nathan, “I have sinned against the Lord.”And Nathan said to David, “The Lord also has put away your sin; you shall not die. 14 However, because by this deed you have given great occasion to the enemies of the Lord to blaspheme, the child also who is born to you shall surely die.” The principle is stated in Lev 5:5 ‘And it shall be, when he is guilty in any of these matters, that he shall confess that he has sinned in that thing; 6 and he shall bring his trespass offering to the Lord for his sin which he has committed, a female from the flock, a lamb or a kid of the goats as a sin offering. So the priest shall make atonement for him concerning his sin. Just look up the word confess in a concordance and one can see this is carried out throughout the scriptures. We walk by faith and not by sight, I just believe that trusting Him by faith is a practice for building up in the faith. The model prayer says forgive us our trespasses as we forgive others their trespasses, seem to me that we are to forgive others like He forgave us and the incident in Matt 18: 21-35 shows that. But I do believe, each person must do as they believe, whatever is not done of faith is sin, says James. But that belief must align itself with the word of God, where there is no obedience and repentance, I side with the word word of God, especially with Proverbs 28:13 He who covers his sins will not prosper,
But whoever confesses and forsakes them will have mercy.