The Protestant doctrine of sola fide (faith alone) teaches that what a man *does* cannot "earn" him salvation, and *only* faith can save him.  

Ironically, the Catholic Church has always (mostly) agreed with this statement.  Man cannot "do" anything to win a spot in heaven. But God has revealed to the Church that it's not merely a statement of faith that saves someone, but faith through grace.  

St. James, in his letter, reminds us that faith makes itself known through our "works".  

"What good is it, my brothers, if someone says he has faith but does not have works? Can that faith save him?  So also faith of itself, if it does not have works, is dead."  (James 2:14)

Our Holy Mother, the Church, exhorts her children to "good works" -- especially the spiritual and corporal works of mercy, because it is through our works that our faith is not only proven, but strengthened by the untold grace we receive through those acts of love.  If we stop, our faith withers,  And the end result is separation from our Maker through our own choosing.  

St. Peter, our first pope, issued two known encylical letters (1 and 2 Peter).  In his second letter, he warns his readers the following: 

"Therefore, brothers, be all the more eager to make your call and election firm, for, in doing so, you will never stumble." (2 Peter 1:10)

Finally, St. Paul says to each one of us:

"work out your salvation with fear and trembling."  (Phillipians 2:12) 

In other words, don't let up.  Keep "doing" the things that nurture your faith, so that you may have the Eternal Life promised through salvation. 

"For God did not send his Son into the world to condemn the world, but that the world might be saved through him."
John 3:17

169 Salvation comes from God alone;

183 Faith is necessary for salvation. The Lord himself affirms: "He who believes and is baptized will be saved; but he who does not believe will be condemned" (Mk 16:16).

620 Our salvation flows from God's initiative of love for us, because "he loved us and sent his Son to be the expiation for our sins" (1 Jn 4:10). "God was in Christ reconciling the world to himself" (2 Cor 5:19).

621 Jesus freely offered himself for our salvation. Beforehand, during the Last Supper, he both symbolized this offering and made it really present: "This is my body which is given for you" (Lk 22:19).

The painting at the top of this page depicts the expulsion of Adam and Eve from the Garden of Eden. All of salvation history stems from this moment of sadness, when our first parents failed the test of fidelity to God's command not to eat of the Tree of Knowledge of Good and Evil.  Our Lord reveals to us through the sacred author that our relationship with Him was irepparably broken through the sin of *pride* -- the same sin which cast Lucifer from heaven. The serpent, though victorious in the initial battle with humanity, is promised his own destruction:
 

"I will put enmity between you and the woman,

and between your offspring and hers;

They will strike at your head,

while you strike at their heel."
(Genesis 3:15)

What were the results of our fall from grace?

• Physical corruption and death entered the world
• Sin became our master, and the devil our accuser.
• The way to the Tree of Life was blocked.  i.e., Heaven was made inaccessible to man.  

Exerpt from Life of Christ, by Venerable Fulton Sheen

The story of every human life begins with birth and ends with death. In the Person of Christ, however, it was His death that was first and His life that was last. The scripture describes Him as “the Lamb slain as it were, from the beginning of the world.” He was slain in intention by the first sin and rebellion against God. It was not so much that His birth cast a shadow on His life and thus led to His death; it was rather that the Cross was first, and cast its shadow back to His birth. His has been the only life in the world that was ever lived backward

[Jesus] does not fit, as the other world teachers do, into the established category of a good man. Good men do not lie. But if Christ was not all that He said He was, namely, the Son of the living God, the Word of God in the flesh, then He was not “just a good man” then He was a knave, a liar, a charlatan and the greatest deceiver who ever lived. If He was not what He said He was, the Christ, the Son of God, He was the anti-Christ! If He was only a man, then He was not even a “good” man.
 

If He is what He claimed to be, a Savior, a Redeemer, then we have a virile Christ and a leader worth following in these terrible times; One Who will step into the breach of death, crushing sin, gloom and despair; a leader to Whom we can make totalitarian sacrifice without losing, but gaining freedom, and Whom we can love even unto death. We need a Christ today Who will make cords and drive the buyers and sellers from our new temples; Who will blast the unfruitful fig-trees; Who will talk of crosses and sacrifices and Whose voice will be like the voice of the raging sea. But He will not allow us to pick and choose among His words, discarding the hard ones, and accepting the ones that please our fancy. We need a Christ Who will restore moral indignation, Who will make us hate evil with a passionate intensity, and love goodness to a point where we can drink death like water.  
                                                          Source:  Sheen, Fulton. Life of Christ. New York, Doubleday, 1958.