it's a growing process in which you are in partnership with God. Those that are saved are seen because of Christ as without spot or blemish however, salvation is a growing process in which we continue to become more like Christ so that His righteousness, HIs spotless perfection is more and more obvious in our lives. It's okay not to be perfect so to speak as long as we are growing ever more into that perfected image through the power of the indwelling HS. It's kind of like God's power mixed with our effort yields an every closer image to the spotless, without blemish Lamb of God. We won't achieve that this side of heaven but that is where the blood of Christ comes into the picture.
Let's try this another way. In the OT if you look into the temple and sacrifices without getting caught up in the legalism what you find is a beautiful picture of Christ's sacrifice for us.
The Holy of Holies was the throne of God and because it was the throne of God there had to be blood placed on it to cover the sins of the people. See, God is so holy that He cannot be in the fellowship of sin...the consequence of sin is death. So if death covered the sin then it was as if there was nothing standing between God and man. Thus fellowship occurred. Christ's blood atonement covers over our sins just as the blood of the lambs covered over the sins of Israel in the OT temple. It is kind of like the sins cannot be seen because the blood covers them. For you and I in the NT covenant it is a blood that covers our sins when we accept it through faith after confessing and repenting of that sin.
Repenting meaning turning from. So basically if you confess all your sins, repent of them with the power of God combined with your efforts, the blood is applied and you are one of the Church that is the bride of Christ. You are without spot and blemish if Christ's blood is applied to your every sin and you allow God to grow you into Christ likeness.
Does that help?