True repentance is coming to that point where you see your puny self up next to the Almighty, Omnipotent, Holy, and Just God and realize you have offended Him, have caused Him pain, have broken His commands, and realize how sinful and filthy you are compared to His perfection, and you despair of that knowing there is no way of fixing the relationship you have broken with Him because of your sin, yet wanting desperately to. You get to the point where you realize there is nothing, not one thing you can do or think or say that can help you. You get to the point where you realize that God alone is the only solution. That He is God, and you are not, and can never be.
Then, and only then, God pours out His grace to you through the finished and victorious work of Christ' death and resurrection.
If you try in any way to think, say, or do anything to bring you back into God's graces, to cause God to pour out His grace, to come into a state of grace, then it is no longer only God's finished work, but your own. And that is sin. And if that is sin, then there was never any true repentance because you have elevated yourself into God's holy position.