A full and complete understanding of everything Jesus accomplished through His passion is the foundation for our boldness. The finished work of Jesus has given us permission to approach God unreservedly about every aspect of our lives. We have received the greatest gift of all, the ability to enter the holy of holies and fellowship with our Creator. We often lose sight of this fact because we allow what happens around us to take our focus off of who we are in Christ Jesus. Salvation is obtained by receiving and believing that Jesus Christ is Lord and that God raised him from the dead (Romans10:9). Our works can not achieve salvation.
We must only receive the gift of salvation. Second Corinthians 3:4–5 clearly teaches us to rely on Christ, and not on our works or abilities, to approach God.
Such is the reliance and confidence that we have through Christ toward and with reference to God. Not that we are fit (qualified and sufficient in ability) of ourselves to form personal judgments or to claim or count anything as coming from us, but our power and ability and sufficiency are from God. [It is He] Who has qualified us [making us to be fit and worthy and sufficient] as ministers and dispensers of a new covenant [of salvation through Christ], not [ministers] of the letter (of legally written code) but of the Spirit; for the code [of the Law] kills, but the [Holy] Spirit makes alive. 2 Corinthians 3:4–6 (amp, italics mine)
We must rely on His finished work so that we can be fit and worthy to work in the kingdom of God. Paul is teaching us that all of our power and abilities come from God. There is nothing within us that is sufficient enough to earn the right to receive from God. It is all given to us by God. The sufficiency we need to live this life is given to us through our belief and confidence in Christ, enabling us to perform whatever is required.