It’s not uncommon for me to receive a question from an anxious Christian (usually a new believer who hasn’t yet experienced God’s faithfulness) who’s worried he might lose his salvation in the future. This is simply not possible. As C.H. Spurgeon explains in his excellent little book All of Grace, our unbreakable union with Christ guarantees our perseverance:

In what the Lord has done, we see strong reasons for our preservation and future glory because the Lord has called us into the fellowship of His Son Jesus Christ. It means into partnership with Jesus Christ, and I would have you carefully consider what this means. If you are indeed called by divine grace, you have come into fellowship with the Lord Jesus Christ, and are joint-owner with Him in all things. Henceforth you are one with Him in the sight of the Most High. The Lord Jesus bare your sins in His own body on the tree, being made a curse for you, and at the same time He has become your righteousness so that you are justified in Him. You are Christ’s and Christ is yours. As Adam stood for his descendants, so does Jesus stand for all who are in Him. As husband and wife are one, so is Jesus one with all those who are united to Him by faith; one by a conjugal union which can never be broken. More than this, believers are members of the Body of Christ and so they are one with Him by a loving, living, lasting union. God has called us into this union, this fellowship, this partnership, and by this very fact He has given us the token and pledge of our being confirmed to the end. If we were considered apart from Christ, we would be poor perishable units, soon dissolved and borne away to destruction; but as one with Jesus we are made partakers of His nature and are endowed with His immortal life. Our destiny is linked with that of our Lord, and until He can be destroyed it is not possible that we would perish.

Dwell much upon this partnership with the Son of God, unto which you have been called, for all your hope lies there. You can never be poor while Jesus is rich because you are in one firm with Him…. You can never fail, for though one of the partners in the firm is as poor as a church mouse and in himself an utter bankrupt who could not pay even a small amount of his heavy debts, yet the other Partner is inconceivably, inexhaustibly rich. In such a partnership you are raised above the depression of the times, the changes of the future, and the shock of the end of all things. The Lord has called you into the fellowship of His Son Jesus Christ, and by that act and deed He has put you into the place of infallible safeguard.

If you are indeed a believer, you are one with Jesus, and therefore you are secure. Do you not see that it must be so? ... Christ and the believing sinner are in the same boat; unless Jesus sinks, the believer will never drown….

So, then, with the utmost confidence let us go forward into the unknown future, linked eternally with Jesus.

As Spurgeon says, “[God] has gone so far in blessing us that it is not possible for Him to run back.” You can never be separated from Christ. The union is done and can’t be undone. You won’t fail because he won’t fail. Forget about your weakness. His strength is all that matters.