From Luke 16:10 and Mere Christianity.
There is never an action which does not shape our character. This is why I try (often unsuccessfully, true) to do my homework, act honorably in computer games (especially when they don’t reward it), not cheat in meaningless games, and not exceed the speed limit. They are all trivial in the breach, but I would argue they are tremendous in a bind. For what you practice, you will do. Sure, no one cares if you kill the peasants, but it is the character that you engender that counts. This is why I hate it when people say “it’s just a game!” It is NOT “just” a game, it is a practice run. Every time you perform, you practice, you prepare for when it really counts. And he who is unrighteous in a very little thing…
…is unrighteous also in much.
I really like practicing ballet!