I think part of the problem that you're having is you presuppose that by accepting Jesus as Lord that not only are all your former sins forgiven but all your future sins are forgiven .too
When it comes to salvation, yes. That is how that foundation is laid by Jesus Christ which can never be removed and how that seal of adoption is not going anywhere for why we are not to grieve the Holy Spirit in us. The works on that foundation will be judged but that foundation remains just as that seal of adoption does too for why even former believers are called t depart from iniquity because He still abides in them..
1 Corinthians 3:10 According to the grace of God which is given unto me, as a wise masterbuilder, I have laid the foundation, and another buildeth thereon. But let every man take heed how he buildeth thereupon.
11 For other foundation can no man lay than that is laid, which is Jesus Christ.
12 Now if any man build upon this foundation gold, silver, precious stones, wood, hay, stubble;
13 Every man's work shall be made manifest: for the day shall declare it, because it shall be revealed by fire; and the fire shall try every man's work of what sort it is.
14 If any man's work abide which he hath built thereupon, he shall receive a reward.
15 If any man's work shall be burned, he shall suffer loss: but he himself shall be saved; yet so as by fire.
16 Know ye not that ye are the temple of God, and that the Spirit of God dwelleth in you?
17 If any man defile the temple of God, him shall God destroy; for the temple of God is holy, which temple ye are.
2 Timothy 2:10 Therefore I endure all things for the elect's sakes, that they may also obtain the salvation which is in Christ Jesus with eternal glory.
11 It is a faithful saying: For if we be dead with him, we shall also live with him:
12 If we suffer, we shall also reign with him:
if we deny him, he also will deny us:
13 If we believe not, yet he abideth faithful: he cannot deny himself.
18 Who concerning the truth have erred, saying that the resurrection is past already; and overthrow the faith of some.
19 Nevertheless the foundation of God standeth sure, having this seal, The Lord knoweth them that are his. And, let every one that nameth the name of Christ depart from iniquity.
20 But in a great house there are not only vessels of gold and of silver, but also of wood and of earth; and some to honour, and some to dishonour.
21 If a man therefore purge himself from these, he shall be a vessel unto honour, sanctified, and meet for the master's use, and prepared unto every good work.
Ephesians 4:30
And grieve not the holy Spirit of God, whereby ye are sealed unto the day of redemption.
When it comes to abiding in Him as His disciples, repentance by His help and by His grace is necessary if desiring to be received by Him as His disciple, the vessel unto honor, the abiding bride of Christ at the rapture event.
Those who do not look to Him for help to depart from iniquity before the Bridegroom comes, will be left behind to die but their spirits will be with the Lord per 1 Corinthians 3:15 & 2 Corinthians 5:7-8 because we will be judged by what we built on that foundation 2 Corinthians 5:9-11 for why and how there are vessels unto dishonor in his House, vessels of wood and earth that did not depart from iniquity per 2 Timothy 2:19-21 that will be resurrected after the great tribulation.
So let us think about that for a minute you have a new Christian that comes to the Lord and all the past sins are forgiven that's correct now the new Christian gets really angry at somebody else and he's told that all his future sins are forgiven all right so that Christian goes out and kills somebody and you know what he's saying to himself it's okay because God has forgiven me.
Why would Jesus teach us the Our Father if all our sins are forever forgiven.
Our Father who is in heaven holy is your name your kingdom come your will be done on Earth as it is in heaven give us today our daily bread and forgive us our trespasses as we forgive those who trespass against us and lead us not into temptation but Deliver Us from Evil amen
I'm sure the King James Bible and a few others have a little different variation of it but it's still the same
Why would we ask the Lord to forgive us our sins if Jesus has already done the forgiveness
It is true that Jesus died on the cross once for everyone sin. But we still need to seek forgiveness from what we do every single day.
1 John 2:1My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous:
2 And he is the propitiation for our sins: and not for ours only, but also for the sins of the whole world.
1 John 1:9 If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.
This is why "holy communion", the confessional booth, going to Mary because Jesus is mad at them & Jesus will not say no to Mary rationalization, and the last rites are totally unnecessary when any Catholic can go straight to Jesus for the forgiveness of sins. Indeed, those Catholic things can be a thief when a Catholic seek forgiveness right away from Jesus Christ when time does not allow for anything else, and yet they believe they cannot come to Him right away and yet He is the only One that can forgive them of their sins and on top of that, cleanse them from all unrighteousness as a result.
Matthew 18:21 Then came Peter to him, and said, Lord, how oft shall my brother sin against me, and I forgive him? till seven times?
22 Jesus saith unto him, I say not unto thee, Until seven times: but, Until seventy times seven.
I believe Jesus is saying that because He knows saved believers will be needing forgiveness from Him on a daily basis as He taught us to pray so why believe something else is required when we should be free to come to Him?.
Matthew 6:9 After this manner therefore pray ye: Our Father which art in heaven, Hallowed be thy name.
10 Thy kingdom come, Thy will be done in earth, as it is in heaven.
11 Give us this day our daily bread.
12 And forgive us our debts, as we forgive our debtors.
13 And lead us not into temptation, but deliver us from evil: For thine is the kingdom, and the power, and the glory, for ever. Amen.
14 For if ye forgive men their trespasses, your heavenly Father will also forgive you:
15 But if ye forgive not men their trespasses, neither will your Father forgive your trespasses.
Reads to me that the Father is readily & willing to forgive & the only stipulation is us being willing to forgive others too. No hurdles of confessional booths, Mary, last rites or "holy communion" to bring that forgiveness of sins about.