What does "Christ alone" and "grace alone" mean for the believer?

Carlton McLeod explains in this video that Christ alone is sufficient. Only by grace alone can we walk with Him. It has to be a work of God through Christ. The whole idea that it is Christ alone and that it is by His grace puts man where he needs to be – at the foot of the cross, totally dependent on the grace and mercy of God alone. 

There is nothing that we can do that can merit salvation. We are all sinners, we all are in need of salvation. It is only by grace alone and Christ alone that we can be saved. 

Ephesians 2:8-9 (NKJV) - "For by grace you have been saved through faith, and that not of yourselves; it is the gift of God, not of works, lest anyone should boast."

It has been this declaration that Jesus is enough, that he is the source, that he is everything, and that only by grace or by grace alone, only by grace can we walk with Him. It has to be a work of the Spirit of God through Jesus Christ. And I think those two things together, I think just the whole idea that it's Christ alone and it's only by His grace. It just puts man where he needs to be, at the foot of the cross, totally dependent on the grace and the mercy of God.