"For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Not of works, lest any man should boast. For we are his workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them."
This scripture lays it out pretty plainly that it is the grace of Christ that saves us "through faith" and that salvation can't be accomplished by our acts. The work that Christ did for us, none of us could ever do for ourselves. It also tells us that we were created to follow Christ in His good works. The Savior is our perfect example "who went about doing good" (Acts 10:38). We were told by Him that the way to show Him our love was to keep his commandments (John 14:15).
Many wonder to themselves "If we are saved by grace and it is a gift from God... Why do those Mormons think that they need to do so much? They go door to door, they have 3 hours of church on Sundays, they serve those around them, and so many other things. Do they feel that faith isn't enough?" Not at all. It is our faith that motivates us to do all the things that we do. I'm sure that nobody told Paul to sit back and relax and just have faith. He was following the commission that Christ had given to the Apostles to preach the gospel. He took it upon himself to exercise his faith in that way. He helped others gain faith in Christ. That is the same mission that our proselyting missionaries are out doing today. Their entire purpose is to invite others to come unto Christ through faith, repentance, baptism, and receiving the Holy Ghost into their lives. They don't serve to mark something off of some sort of checklist that will get them to Heaven.
Lets look at James 2 for a moment where it has this to say: "Even so faith, if it hath not works, is dead, being alone" (James 2:17). Let's cross reference this to the Savior's great sermon on the mount where He said:
"Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven... Therefore whosoever heareth these sayings of mine, and doeth them, I will liken him unto a wise man, which built his house upon a rock... And every one that heareth these sayings of mine, and doeth them not, shall be likened unto a foolish man, which built his house upon the sand"
(Matthew 7:21, 24, & 26 italics added).
All these scriptures, along with others, are the basis for why Mormons seem to be preoccupied with works when, to us, we are only trying to do all the things that Christ has commanded us. "If ye love me, keep my commandments" (John 14:15). Which commandments? All of them. Of course we aren't going to be perfect, that is why He came "to save the world from sin" (3 Nephi 9:21) He commanded men to repent and be baptized, He commanded us to love our neighbors, He commanded to preach the gospel, and on and on and on. His words and commands never cease. He has given us many things to work on in this life that will help us to become more like Him and it is our faith in Christ motivates us to become like Him.
No matter what good things we accomplish in this life, we cannot for a moment think that we are making our own path into heaven. Christ made the path, Christ made the rules. We follow Him, His commandments, and His example. That is the way to salvation through His grace. I hope this has cleared up any questions any may have about why our church seems to "work" so much.
I know that obedience to God's commands is the way to happiness with Him in this life and in the next, I know that when we have true faith that we will desire to do good to others as He would, for this is how we show Him our love. I know Christ lives. I know He speaks today. I know this because I have exercised my faith and done my best to follow Him. I know that as we find a balance of faith and works we will be happy followers of our Savior Jesus Christ. For He is the way to Salvation. I leave this with you in His name, Jesus Christ. Amen.