Salt of the Earth.

What does it mean to be the salt of the Earth? My church history is a repetitious cycle of bible stories, parables, and anecdotes. I remember being taught to be the "salt of the Earth" as it says in Matthew 5:13-16. I have come to the conclusion that this passage must be talking about the lukewarm Christian. It is a warning to not let one's relationship with Christ lose its flame. Salt, once it loses its saltiness can not be restored to its original taste. At this point, salt is completely useless. Matthew 25:30 says,  "Worthless servants will be thrown outside, into the darkness, where there will be weeping and gnashing of teeth." What a horrible way to spend eternity! This is why we are encouraged to be salty. 

PS i commented on Jasmine's post.