A hard question, faced honestly
Can I Lose My Salvation?
Christians hold this differently in good faith, but the note the New Testament sounds most often is security, not anxiety. Jesus said of his sheep, I give unto them eternal life; and they shall never perish, neither shall any man pluck them out of my hand. Paul was persuaded that nothing in all creation could separate us from the love of God in Christ. Salvation rests on God's grip on you, not your grip on him, which is why a genuine believer can have real assurance rather than living in fear.
“And I give unto them eternal life; and they shall never perish, neither shall any man pluck them out of my hand.”John 10:28
“For I am persuaded, that neither death, nor life, nor angels, nor principalities, nor powers, nor things present, nor things to come,”Romans 8:38
“Being confident of this very thing, that he which hath begun a good work in you will perform it until the day of Jesus Christ:”Philippians 1:6
Let's not dodge it
This question often comes from a tender conscience, someone afraid that a bad day, a doubt, or a fall has undone everything. That fear is worth answering gently. It can also come from watching people seem to walk away from faith entirely, which raises a real puzzle. So the honest answer holds two things: the deep security the New Testament offers to those who truly belong to Christ, and its equally real warnings against drifting, presuming, and turning back. Both are in the Bible, and neither should be erased.
How Christians have answered
The strongest thread is assurance. Jesus promises his sheep will never perish and that no one can snatch them from his hand. Paul says God, who began a good work in you, will finish it, and that nothing can separate us from his love. At the same time, Scripture warns believers to keep following, take heed, and not fall away, warnings that God actually uses to keep his people persevering. Many Christians reconcile these by saying that those who are truly his are kept by him, and that the warnings are among the means he uses to keep them. Either way, the point is not to make you anxious but to make you cling to Christ.
Where it leads
The center of your security is not the strength of your faith but the strength of the Savior your faith rests on. You are held by hands that were nailed to a cross for you, and those hands do not slip. If you are afraid you have gone too far, that very fear is often a sign the Shepherd is still holding on. Come back to him honestly; his promise is that he will in no wise cast out anyone who comes. Assurance is not presumption when it rests on him. It is the settled rest he wants his children to have.
Questions people ask
Do Christians agree on this?
No, and sincerely so. Some traditions emphasize that a true believer is eternally secure; others stress the warnings against falling away. Both are trying to be faithful to Scripture, which contains strong assurances and real warnings. All agree salvation is God's gracious work in Christ, received by faith.
What if I have doubts or have failed badly?
Doubts and failures are not proof you are lost; the New Testament is full of believers who doubted and fell and were restored. Salvation rests on God's faithfulness, not your perfect record. Turn back to Jesus honestly, and trust the promise that he will not cast out anyone who comes to him.