Pride

C.S. Lewis had it right when he wrote that, of all the sins, Pride is the most deadly. It is always on the outskirts of what we do, lurking in the shadows. Do a good deed and see how quickly it comes up, whispering "I really am good for doing that" or "I'm so much better than so-and-so." We must always be on our guard against this one, for it is like the wolf in sheep's clothing. All other sins, as bad as they may be, are seen for what they are. This will lead you over time to think that you are your own god. If allowed to run its' course, it will destroy our very spiritual life from the inside out.