What do we know? We know people, places, facts, objects, languages, song lyrics, truths, and so much more. It's one of the blessings that accompany the wonder that is the human brain. We know so much and have the capability to know so much more! It's why they make us go to school...so they can stuff more knowledge into our brains.
I think it makes a difference when we know things. For example, I know that I am a beautiful daughter of God. Knowing this makes me walk more confidently, helps me ignore what the rest of the world is trying to tell me, and keeps me feeling happy. I remember when I didn't know this, and it was a terrible feeling; I didn't know my own identity, and it held me back. Now, I can move forward, all because I know this one thing, this one truth.
I also know that "whatever principle of intelligence we attain unto in this life, it will rise with us in the resurrection. And if a person gains more knowlegde and intelligence in this life through his diligence and obedience than another, he will have so much the advantage in the world to come" (Doctrine and Covenants 130:18-19). Basicslly, whatever we come to know now will stay with us for time and all eternity, both the good stuff and the bad stuff.
So let's make an effort to know all the good stuff we can, since it's always going to stick with us and will help define and strengthen us in both our troubling times and in our everyday lives.