I truly wish that I understood what is meant when you say us being sinless. Once we have sinned, we cannot turn back the clock and erase it. We are tarnished and stained, even if a person only commits one single sin. (I doubt that has ever been, but just for illustration.) We can "sin no more", but we can never become sinless.
But our sins can be cleansed, and the demands of justice have been satisfied by Christ, who purchased us if we repent. It is impossible to cleanse us if we still wallow in the muck of sin that stains us. We must choose to deny ourselves and come out of the muck. We must loose the desire for sin, and that can only happen if something takes its place, namely a love for God with all our heart, mind, might and strength. That love will only develop if we prime the pump, so to speak. If you do not fully understand what it means to prime the pump, google it. The works that Jesus gave us to do are, by design, the enabling primer. With devoted attention to His works, we can become converted to the joy that these works bring us, if we will allow the refining influence of works to remove our pride. That joy will replace any and all desire to sin. Jesus said that when we sin, we are the servants of sin. That is bondage! We must be rescued or "saved" from that bondage!
I said that those who chose to believe, and demonstrate that belief by doing the will and works of God are separated by those who have wishy washy belief who deny that works are necessary. (No offense intended, as I realize it could come across that way. The real offense would be to not speak in truth, and this is what I understand as truth.)
We are not saved until the end, because enduring to the end is a written definition of salvation. We can have assurance that we are on the protected path that leads us to salvation, but we must remain on that path. Sin takes us off that path, and if not repented of will alter our understandings of the things of God as well.