Man can commit sin even after becoming a Christian. That’s why God’s grace are new every morning.
It is not that they want to sin wilfully, but like what Apostle Paul said,’…what I hate to do, that I do’. (Romans 7:15)
As a Christian, I will try to live my life without ever sinning again. I would want to, it’s possible, but not easy. By God’s grace, I might be able to be without sin ever again, but hey, if I do fall, I know that God is gracious and merciful IF I were to confess and repent.