In C.S. Lewis' The Screwtape Letters the devil, Screwtape, advises his nephew, Wormwood saying the following: "...The humans live in time but our enemy (God) destines them to eternity. He therefore, I believe, wants them to attend chiefly to two things, to eternity itself, and to that point of time which they call the Present. For the Present is the point at which time touches eternity."
It is so important for our eyes to be fixed on eternity because if we work toward eternity, we will accomplish things that have lasting value wherever we may be- at work, at church, at home with our families, with a friend having coffee, or talking with our kids' teachers at school.