Three Quotes by C.S. Lewis from Mere Christianity:
We might think that, provided you did the right thing, it did not matter how or why you did it — whether you did it willingly or unwillingly, sulkily or cheerfully, through fear of public opinion or for its own sake. But the truth is that right actions done for the wrong reason do not help to build the internal quality or character called a ‘virtue,’ and it is this quality or character that really matters.
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. To be the one kind of creature is heaven: that is, it is joy and peace and knowledge and power. To be the other means madness, horror, idiocy, rage, impotence, and eternal loneliness. Each of us at each moment is progressing to the one state or the other.
Remember that, as I said, the right direction leads not only to peace but to knowledge. When a man is getting better he understands more and more clearly the evil that is still left in him. When a man is getting worse, he understands his own badness less and less. A moderately bad man knows he is not very good: a thoroughly bad man thinks he is all right.