Reason #17: They have an unhealthy fear of the future.
2 Timothy 1:12 says, “For this reason I also suffer these things; nevertheless I am not ashamed, for I know whom I have believed and am persuaded that He is able to keep what I have committed to Him until that Day.” Ecclesiastes 3:11 tells us, “He has made everything beautiful in its time. In addition, He has put eternity in their hearts, except that no one can find out the work that God does from beginning to end.”
People who doubt their salvation wonder and are fearful that God may not keep them. For many people, the whole concept of eternity is deeply troubling. People who do not doubt their salvation have absolute confidence and faith in the power of God to keep them saved. For more assurance read this.