I will attempt to answer this question by first making a reference to the classic motion picture, Disney's Mulan. One of my favorite songs in that movie is called something along the lines of, "A Girl Worth Fighting For." In this song the soldiers all sing of a girl who would motivate them to fight with honor, or in other words they speak of what motivation would give them a greater resolve to conquer. What makes the difference in someones determination or resolve is there motivation. Sometimes in our lives it is a beautiful child of God that motivates us to be better people, but that only lasts as long as that person shows us some interest. While it is a good motivator for a moment may I suggest a better source of motivation. The motivation I speak of is the love for God. When you do anything out of love for another person, it only lasts as long as that love is being reciprocated, so the fact that God's love for us is unconditional and unfailing makes it a great place to ground our actions.
So, how do we go about showing our love for God? Consider the clear and concise council given by Christ himself, "If you love me, keep my commandments." (John 14:15) Not only has Christ granted unto us the ability to change, but he has also showed us what we can change. As we strive to live the commandments we will not be left uncertain as to what we can do to become better people, and not only that, but Christ will also help us as we strive to live according to His will.
Pictures are courtesy of LDS.org