19 Lay not up for yourselves treasures upon earth, where moth and rust doth corrupt, and thieves break through and steal;
20 But lay up for yourselves treasures in heaven, where neither moth nor rust doth corrupt, and where thieves do not break through nor steal.
21 For where your treasure is, there will your heart be also.
(3 Nephi 13:19-21)
In this chapter, the Savior has just given three examples of people participating in righteous activities who failed to receive the blessings from those activities. The activities were: charitable giving, praying, and fasting–all of which we are commanded to do. Why did they fail to receive the full reward? Because in all three cases, their primary motivation was to gain power or status here on earth among their peers. The goal was short-term and temporary, and so the action did not produce the permanent benefit it might otherwise have.
I want to set my sights higher. I want to participate in righteous activities without regard for the short-term reward (without caring whether others are aware of what I have done, for example.) I want to be focused on the eternal value of righteous activities, so that I can experience their full reward.