You've been meaning to learn French. You'd love to play the piano. How great would it be to really know how to cook? You'll read Mastering the Art of French Cooking, and, man, you'll master it. You can even work on your French at the same time! Resolving to learn something new is exciting: the world is full of fascinating facts, skills and talents. And the process of discovering them, not just the end result, is enjoyable and rewarding.
At least, for a while. Soon you remember there's a reason you haven't learned all this yet. French is too hard to pronounce. Piano takes too much practice. Ordering out is just so much easier than cooking. You'll do it ... when you have more time.