A sneak peak... at the Plan of Salvation

From teachings of The Prophets of the Church: Joseph Smith, Chapter 17:
We came to earth to obtain a body, to gain knowledge, and to overcome through faith.

“All men know that they must die. And it is important that we should understand the reasons and causes of our exposure to the vicissitudes of life and of death, and the designs and purposes of God in our coming into the world, our sufferings here, and our departure hence. What is the object of our coming into existence, then dying and falling away, to be here no more? It is but reasonable to suppose that God would reveal something in reference to the matter, and it is a subject we ought to study more than any other. We ought to study it day and night, for the world is ignorant in reference to their true condition and relation [to God].”

Why should the knowledge of the Plan of Salvation be so important to us?