This is what all the complex theological statements from Paul have been about: salvation is nothing to do with the saved person, but it's all from God! Why did He do this? To show the limitless stretch of His grace and because we are His masterpieces. Yes, fallen, broken, twisted masterpieces, but still, once redeemed by the grace He showers upon us, we can do what He originally intended us to do. Our part in our salvation is simply to accept it. Nothing more, nothing less. It is vital for us all to understand that when we disobey God and go our own way we don't so much break God's Law as break His heart and that can only be restored by His free forgiveness and this He demonstrated when He sent His Son to be the Saviour of the world (John 3 v 16, 1 John 4 v 14). The great Emperor Constantine was converted to Christianity, but waited until he was on his deathbed to be baptised. He did this so that he wouldn't have the opportunity to sin before he died, proving that he understood about his own natural waywardness in a way that some Christians do not, but demonstrating also that he underestimated God's grace, which isn't a one off gift to us, but is continual, ever flowing ever free, otherwise the sacrifice that Christ made has only limited value. I became a Christian when I was eleven and baptised at 16. If Constantine's view was correct I would now be an utterly hopeless case.