The gospel is not a “one-time” truth, but an everyday truth, as Jerry Bridges has articulated:

To preach the gospel to yourself, then, means that you continually face up to your own sinfulness and then flee to Jesus through faith in His shed blood and righteous life. It means that you appropriate, again by faith, the fact that Jesus fully satisfied the law of God, that He is your propitiation, and that God’s holy wrath is no longer directed toward you.

To preach the gospel to yourself means that you take at face value the words of Romans 4:7-8 —

Blessed are they whose transgressions are forgiven, whose sins are covered.
Blessed is the man whose sin the Lord will never count against him.

It means that you believe on the testimony of God that “Therefore, there is now no condemnation for those who are in Christ Jesus (Romans 8:1). It means that you believe that Christ redeemed [you] from the curse of the law by becoming a curse for [you], for it is written: ‘Cursed is everyone who is hung on a tree’ (Galatians 3:13). It means that you believe He forgave you all your sins (Colossians 2:13) and now “[presents you] holy in his sight, without blemish and free from accusation” (Colossians 1:22).…

It means that you dwell upon the promise that God has removed your transgressions from you as far as the east is from the west (Psalm 103:12), that He has blotted out your transgressions and remembers your sin no more (Isaiah 43:25). (See also Isaiah 38:17 and Micah 7:19 for other assurances of God’s forgiveness). But it means that you realize that all these wonderful promises of forgiveness are based upon the atoning death of Jesus Christ.

It is the death of Christ through which He satisfied the justice of God and averted from us the wrath of God that is the basis of all God’s promises of forgiveness. We must be careful that, in preaching the gospel to ourselves, we do not preach a gospel without a cross. We must be careful that we do not rely on the so-called unconditional love of God without realizing that His love can only flow to us as a result of Christ’s atoning death. [The Discipline of Grace, pp. 58-9; my emphasis.]