Election is made sure based upon God's foreknowledge and our responsibility. Election in Christ was before time began. Yet, we are responsible to receive Jesus Christ by faith (John 1:11-12). Our call and election is made sure, as we grow in the grace and knowledge of our Lord Jesus Christ (2 Peter 1:10; 3:18). Our election is made sure in Christ alone.
The Bible doctrine of election has two sides. There is the divine side and the human side. God foreknew us in Christ before the foundation of the world (1 Peter 1:2). However, your call and election in Christ is made sure in time (2 Peter 1:10).
God foreknew us in Christ (Romans 8:29-30). Yet, we must be born again at a certain point in time. God foreknew the time of our conversion, but we must receive God's grace through repentance and faith in the Lord Jesus Christ (Galatians 1:15; 2:20). Our election is made sure in Christ, when we repent and believe on the Lord Jesus Christ (Acts 16:30-31).
The debate over election continues, as some look at the doctrine from God's perspective, and others look at it from man's view. If we begin with God, election is whom God foreknew in Christ. If we begin with man, election includes all who believe the gospel of Christ. Our election is in Christ, according to the foreknowledge of God. Yet, your election is made sure by faith in Christ.