A consistent theme to Lewis's works is the idea of becoming like Christ rather than just doing Christian things.  The devils in The Screwtape Letters work to make sure any virtuous action is done for the wrong reasons.  If the right things are done for the wrong reasons, they are of little help to us.  Those who return to Hell in The Great Divorce do so because they refuse to become like God - that there is something about being themselves they won't give up.  The irony here is that by giving up those parts of ourselves that hold us back and choosing therefore to become more like God we become even more ourselves.  We are each divinely unique and when we focus on becoming like God we truly find who we are.

Lewis most clearly elaborates this concept of becoming in Mere Christianity.  He goes on to tell of various sins discussing why each one is important.  And then he gets to Pride - what he calls the worst of all the sins.  He describes Pride as the only Spiritual sin.  All our other sins come through some perversion or distortion of natural impulses and drives.  But Pride - that is the idea that we are better than others.  We get no satisfaction out of actually being smart, or good looking but in thinking smugly that we are better at those things than others.  This distinction is what makes Pride so dangerous.  It literally rips all our relationships to shreds.  We cannot feel Godlike love because we are too busy judging or disdaining others.  Once we let go of ourselves and focus on others and becoming like God, He takes the helm in our lives and the real journey really begins.

We are not the sum of our actions.  Certainly each choice is going to leave a mark.  But it is how we choose to look at each choice - whether we choose to grow, forgive and learn - that defines us in the end.  Christ invites us to come unto Him and become as He is.  That is the only thing that matters.