I read on a blog recently that the Christian should always be aware that he is redeemed, yet a sinner.  Yes, a common and simple idea, I know.  But, consider these words from Tim Keller on this subject:

“The Christian gospel is that I am so flawed that Jesus had to die for me.  This leads to deep humility and deep confidence at the same time.  It undermines both swaggering and sniveling.  I cannot feel superior to anyone, and yet I have nothing to prove to anyone.  I do not think more of myself nor less of myself.  Instead, I think of myself less.  I don’t need to notice myself – how I’m doing, how I’m being regarded – so often…His grace both humbles me more deeply than religion can (since I am too flawed to ever save myself through my own effort), yet it also affirms me more powerfully than religion can (since I can be absolutely certain of God’s unconditional acceptance).”

-From The Reason for God (p. 181)