People often think of Christian morality as a kind of bargain in which God says, "If you keep a lot of rules, I’ll reward you, and if you don’t I’ll do the other thing." I do not think that is the best way of looking at it. 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 Heaven 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 at each moment is progressing to the one state or the other. – C. S. Lewis
I know there are things that if I choose to do them, I will never be the same. I believe we have all had that "after this, I will never be who I was" type of experiences. We knew that if we stepped over the line, or took the plunge, or ate the fruit, we would never be the same. I believe that is what C. S. Lewis is hinting at here. Each choice has a consequence, not just a what happens type of consequence, but also a consequence of being. Our choices have the power to change us.
I believe this is what John Wesley meant when he talked about the dispositions of the heart. As we choose to follow God and God’s way, the dispositions of our heart are changed toward the good, or God. If we choose to not follow, to allow sin to reign in our hearts and lives, well, that changes our dispositions too. Choosing to follow will transform our heart from a selfish, sinful disposition, to one that is characterized by loving God and loving others.
Practicing the means of grace (spiritual disciplines) is a way we choose to allow the dispositions of our heart to be transformed. Wesley taught that the means of grace conveyed God’s grace into the life of the individual. When we practice spiritual disciplines, we are choosing to have our heart turned toward God and transformed by God’s grace. Therefore, the disciplines are not optional practices if one has time, but essential practices if one is wanting the dispositions of the heart transformed.