From the LCMS website:
QUESTION: Can you lose your salvation, and, if you can, what do you need to do to regain it again?
ANSWER: The Lutheran Church—Missouri Synod believes and teaches that it is possible for a true believer to fall from faith, as Scripture itself soberly and repeatedly warns us (1 Cor. 10:12; 1 Peter 5:8; 2 Peter 3:17; Heb. 2:1-3, 3:12-19, 6:4-8, etc.).
Such warnings are intended for Christians who appear to be lacking a right understanding of the seriousness of their sin and of God's judgment against sin, and who, therefore, are in danger of developing a false and proud "security" based not on God's grace, but on their own works, self-righteousness, or freedom to "do as they please."
By the same token, the LCMS affirms and treasures all of the wonderful passages in Scripture in which God promises He will never forsake those who trust in Christ Jesus alone for salvation (John 10:27-29; Rom. 8; Heb. 13:5-6, etc.).
To those who are truly repentant and recognize their need for God's grace and forgiveness, such passages are powerful reminders of the true security that is ours through sincere and humble faith in Christ alone for our salvation.
A person may be restored to faith in the same way he or she came to faith in the first place — by repenting of his or her sin and unbelief and trusting completely in the life, death and resurrection of Christ alone for forgiveness and salvation.
Whenever a person does repent and believe, this always takes place by the grace of God alone and by the power of the Holy Spirit working through God's Word in a person's heart.
