We simply have a choice to receive or reject. Sin is part of our being since the fall of mankind, and it is with us everyday. The Apostle Paul had a problem with it too, just as we all do. If we had any ability to save ourselves, or keep ourselves saved, we sure would not need the Lord. And He would not have needed to make atonement with His blood for us.
Eternal life is exactly that - eternal.
It is not something we get after death, but only while we are alive. Therefore our salvation is as secure as God himself. If thou be the Christ, tell us plainly. But ye believe not, because ye are not of my sheep, as I said unto you. I and my Father are one.