In my CS Lewis reader, Lewis says that Christians often think about the consequences of choices either bringing reward or punishment from God. He suggests another way to look at our choices (entry for 17 March):
I would much rather say that every time you make a choice you are turning the central part of you, the part of you that chooses, into something a little different from what it was before. And taking your life as a whole, with all your innumerable choices, all your life long you are slowly turning this central thing either into a heavenly creature or into a hellish creature: either into a creature that is in harmony with God, and with other creatures, and with itself, or else into one that is in a state of war and hatred with God, and with its fellow-creatures, and with itself. (From Mere Christianity)
Does this not help us consider which creature we are forming as we make our many mindless choices every day?
Musings on Faith and Psychology 
In a similar vein, I’ve heard people describe prayer and hearing from God as a series of road signs (ski flags, etc…). That each time we plow right through one, it’s not that it disappears entirely, it’s that we are able to see it a little less clearly. Over time, if we keep plowing through them we suddenly find we can’t hear God at all.
I think this fits with Lewis’ view – each choice we makes brings us a bit closer (or further) from harmony with God.
Makes you think twice before thinking “it doesn’t really matter this time.”
I remember reading this in “Mere Christianity” and it really resonating with me. My only concern however is that the thought by itself can lead to a deficient mindset, thinking that my choices make me who I am.
It’s hard to balance the truth that our choices matter with the truth of grace and my inadequacy, and at times I know I’ve used Lewis to bolster my own prideful ways of increasing my self esteem and relying less on God and more on my choices.
Of course, this problem really lies in me, but I make the comment because I think sanctification (what Lewis is really talking about) is a very difficult truth to live out in our hearts. So often I don’t want grace and forgiveness for my poor choices. Rather, I want admiration and esteem from God and others for my good choices…