One of the saddest phrases I have come across during my reading is “and they began to disbelieve” (Helaman 4:23). Speaking of the Nephites, the Book of Mormon writer summarizes their behavior in the lead up to their loss of faith and Gospel knowledge.
This phrase highlighted for me how critical it is to be actively engaged in your faith. Belief takes work. It is a choice we make to believe in the Gospel or not, to believe in Jesus Christ, to believe that there is life after death. Because many of the Nephites made choices to disobey the commandments, to murder, rob and steal, they, in effect, chose not to believe.
Keeping the commandments, serving others, participating in the Church all foster belief. That kind of action reflects a deliberate choice to believe; it is so important to actively growing faith in Jesus Christ.