"If we do not understand how it is that we as sinners are declared right before a holy God (which is what it means to be “justified”), we may not only misunderstand the gospel–and therefore risk standing before God on the day of judgment expecting that our own righteousness will be sufficient–but we will miss out on the wonderful comfort which this doctrine provides for us.
The good news is that as justified sinners–our sin has been reckoned to Christ, and Christ’s righteousness has been reckoned to us (Romans 5:12, 18-19)–we now possess the greatest gift imaginable, a conscience free from fear, terror, and dread (2 Tim. 4:18).
The knowledge that our sins are forgiven and that God is as pleased with us every bit as much as he is with his own dear Son (2 Corinthians 5:21), not only quiets our conscience and creates a wonderful sense of joy and well-being, but it also provides powerful motivation to live a life of gratitude before God (2 Corinthians 1:3-7). In fact, understanding this doctrine is the only way we will be able to give all glory and thanks to God, which is the ultimate goal of our justification."