We can fall away.
Salvation is not finalized till our probation closes. It can be secured and we can have assurance but while the choice is there we can turn away from salvation.
Consider Jesus’ parable of the sower, which describes the gospel seed being spread on different types of soil. Notice what happens when the truth falls onto one type of heart:
Some fell on stony places, where they did not have much earth; and they immediately sprang up because they had no depth of earth. But when the sun was up they were scorched, and because they had no root they withered away (Matthew 13:5, 6).
Now, if the seed “immediately sprang up,” it means these people welcomed it into their hearts. They believed what they heard, and the seed sprouted. Thus, if it “withered away,” something that was once living had died. That means some people who have received salvation at some point lost it because they did not grow deeper roots in Christ.
A Bible example of someone who was chosen by God and even Spirit-filled, but then fell away, was King Saul. He was not picked through a general election, but was chosen by God. Did the Lord choose Saul to make an example of him and then cast him away? No! God chose this Benjamite because he was the Lord’s choice. At first Saul was filled with the Spirit and even prophesied, but he allowed pride to spring up in his heart, grieved away the Holy Spirit, and then lost his salvation.
Jesus makes it clear in His message to the church of Sardis that if the people did not repent and turn from their bad behaviour, they would lose their salvation. “He who overcomes shall be clothed in white garments, and I will not blot out his name from the Book of Life; but I will confess his name before My Father and before His angels” (Revelation 3:5).