I'm nearly halfway through C. S. Lewis's Mere Christianity. In chapter 4 of Christian Behavior, the third section of the book, his comments on our choices are insightful:

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 into a heavenly creature or 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 is progressing to the one state or the other.

p. 87