Regarding the idea of sacrifice (see also Lesson 3-28, "Consecration and Sacrifice"):
Elder Quentin Cook's talk, "Hope Ya Know, We Had a Hard Time" - the idea that being a member of the Church should be hard, that we do hard things as a people and within our families. We work hard, we value labor, we make financial sacrifices/tradeoffs to pay tithes and offerings, we accept callings/assignments which are hard, we prioritize the gospel above all else, giving up things that we highly prize in order to prove our worthiness, devotion, and love of God. The lesson's "stamp collection story" is a telling one, I think - President Kimball's remark that the prospective missionary would be blessed and would learn an important lesson from selling the one thing of value that he owned and prized in order to go on a mission. While decisions we make are rarely so clear-cut as that one, I think the principle of that story suggests us a lot about who we are as a people.