It is true that if sin could rob us of salvation, a sin Jesus Christ paid for with His own blood, then it would be best to come to faith in Christ and then immediately die. It is good, however, that God is faithful to His covenant, and the blood of Christ cleanses us of all sin, of all unrighteousness. We are justified our entire lives, for we have a High Priest with a priesthood that lasts forever, and He is the eternal sacrifice for our sins. The last sacrifice. Which is why we can preach the Gospel to the unsaved and not sacrifice an animal for their sins, because Jesus is their sacrifice too (propitiation for the sins of the world).
Salvation is by grace through faith. Sinless perfectionism is not the means to our salvation, for then it would be a striving work and a wage due. Rather, God has imputed Jesus' righteousness to us and has justified us. His blood has granted us the remission of our sins (all of them, any one that you may commit). Why? As it says in 1 John 2, we have an Advocate with the Father, Jesus Christ the righteous. It is through Christ and Him crucified that we are saved. No condemnation for those that are in Jesus Christ.