If I am following your line of thinking, then you belief that if you have been forgiven by Christ of your sins you may then go ahead with sinning?
When did I say that? Christians are not sinless 100% of the time, but they should sin less. Do you teach sinless perfection? 1 John 2:1 My little children, these things I write to you, so that you may not sin. And if anyone sins, we have an Advocate with the Father, Jesus Christ the righteous. 2 And He Himself is the propitiation for our sins, and not for ours only but also for the whole world.
I think scripture tells us that we are to give our will to sin to Christ when we ask forgiveness. I think that is what scripture means by repent, and often the command to repent is given with telling us Christ forgives.
To repent means to change your mind and the new direction of this change of mind is faith in Christ for salvation. (Acts 11:17,18; 20:21) Two sides to the same coin. This change of mind also results in a change of actions, which is the fruit of repentance. (Matthew 3:8; Acts 26:20)
You say no one that is born of God practices sin, but if you look around you it shows people who were once Christian and have decided not o be any more.
Don't confuse "nominal" Christians with genuine Christians. 1 John 3:9 clearly states that
no one who is born of God practices sin.. but you say, those who are born of God practice sin and lose their salvation, which is not what John said. There are genuine Christians and there are "nominal" Christians. There are genuine believers and there are make believers, as John points out. (1 John 2:19)
The Lord is truth, and we can check on our understanding of that truth by seeing how it works in our world. To say that once a Christian always a Christian is to deny that Christians are still given free choice.
Believers exercised their free choice upon receiving Christ through faith and continuing to trust in Christ for salvation. To say that genuine Christians don't remain Christians is to deny God's preservation of His saints. (Psalm 37:28; 1 Peter 1:5; Jude 1:1) Those who teach salvation by faith + works typically oppose preservation of the saints.