"I believe in Christianity as I believe that the sun has risen: not only because I see it, but because by it I see everything else."
It is so easy to view Christianity as something to be taken on and off like an old sweater. Something that is comfortable, but gets kinda scratchy if we leave it on for too long. Christianity, however, is not something to be compartmentalized. Our relationship with God should be central. It should be our motivation for every action; our reason for every behavioral pattern; and our only lens with which we see the world. We cannot separate God from our relationships. We cannot separate God from our academic endeavors. We cannot separate God from our jobs. We cannot - and really, should not be able to - separate God from any part of our lives. Every aspect of our lives should go back to the question, "How is this promoting the glory of God?".
Instead of viewing our lives as revolving around Christ, we see Christ as some sort of "addition". Something that we have to "work into" our already jam-packed schedules. But Christianity, as C.S. Lewis points out, is not something to only see and admire, it is something to see with: something to affect every part of us.