If you are saved, you are saved. Period.
If you are born again into the family of God, you cannot be unborn.
Nor can you walk away, for you do not have the heart that would allow you to walk away. You have a new heart. That is what being born again means.
LindaBee2, if our salvation depends upon us enduring, then none of us would be saved. Our salvation depends upon Christ and Him alone. What we run the race for, what we endure for, is His approval, not His acceptance. Not everyone will hear "Well done, good and faithful servant" even though they be believers.
If you look at Matthew 5:19, you will find that even those who break the law and TEACH others to do so may end up in heaven, but "will be called least."
So it is not a matter of sinning at all, for all sins have been atoned for on the Cross. It is a matter of believing on the Lord Jesus Christ, and this is not simply intellectual acknowledgement, for as James says, even the demons go that far! In the Bible, 'believe' means a change of direction for your life -- you follow what you believe in.