All who persevere do so because it is by the will of God, according to the will of God.
"For it is God which worketh in you both to will and to do of his good pleasure." -- Philippians 2:13
You go ahead and worry. As for me and mine, I'll rest assured in His promise not to let go.
When combined with Assurance (and/or how one knows one is elected) it becomes circular.
I should have made that more clear.