It is a false doctrine that sins are forgiven when we ‘receive’ Christ. All past sins are forgiven when we are baptised into Christ by immersion in water.
Acts 2:38 Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins…
Acts 22:16 And now why tarriest thou? arise, and be baptized, and wash away thy sins, calling on the name of the Lord.
Without baptism there is no remission of sins.
1 Peter 3:21 The like figure whereunto even baptism doth also now save us (not the putting away of the filth of the flesh, but the answer of a good conscience toward God,) by the resurrection of Jesus Christ:
Submitting to baptism is the first work of faith. Jesus insisted on being baptised even though he had no sins to be remitted. He did it because this is the way ordained by God ‘to fulfil all righteousness’.
Matthew 3:15 And Jesus answering said unto him, Suffer it to be so now: for thus it becometh us to fulfil all righteousness. Then he suffered him.
Baptism was a vital part of the commission:
Matthew 28:19 Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Spirit:
Mark 16:16 He that believeth and is baptized shall be saved…
Acts 2:41 Then they that gladly received his word were baptized: and the same day there were added unto them about three thousand souls.
Acts 8:12 But when they believed Philip preaching the things concerning the kingdom of God, and the name of Jesus Christ, they were baptized, both men and women.
Baptism represents dying with Christ and rising again to a new life.
Romans 6:3-7 Know ye not, that so many of us as were baptized into Jesus Christ were baptized into his death? 4 Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life. 5 For if we have been planted together in the likeness of his death, we shall be also in the likeness of his resurrection: 6 Knowing this, that our old man is crucified with him, that the body of sin might be destroyed, that henceforth we should not serve sin. 7 For he that is dead is freed from sin.
The new life is to be lived by Christ’s commandments.
John 15:14 Ye are my friends, if ye do whatsoever I command you.
John 14:15 If ye love me, keep my commandments.
John 15:10 If ye keep my commandments, ye shall abide in my love; even as I have kept my Father’s commandments, and abide in his love.
When we live by Christ’s commandments we ‘live in the Spirit’ and ‘walk in the light’. We cannot live a sinless life. If we 'walk in the light', those sins which we commit after baptism will be forgiven by confession in prayer.
1 John 1:7-9 But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin. 8 If we say that we have no sin, we deceive ourselves, and the truth is not in us. 9 If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.
Paul writes to the Colossians about the state following baptism. We are buried in simulated death and so freed from past sins. We are quickened (made alive) by rising out of the waters of baptism.
Colossians 2:13-14 And you, being dead in your sins and the uncircumcision of your flesh, hath he quickened together with him, having forgiven you all trespasses; 14 Blotting out the handwriting of ordinances that was against us, which was contrary to us, and took it out of the way, nailing it to his cross;
The Law of Moses (handwriting of ordinances) which condemns us to death has been annulled by the death and resurrection of Christ. Christ fulfilled the Law and took it out of the way.
Salvation is no longer by the Law, but by faith in Christ which requires obedience to his commandments.
Romans 3:20 Therefore by the deeds of the law there shall no flesh be justified in his sight: for by the law is the knowledge of sin.
Romans 3:28 Therefore we conclude that a man is justified by faith without the deeds of the law.
I hope you find this helpful.