Dishwasher

If you have it, you don't need it. If you need it, then you don't have it. If you have it, you need more of it. If you have more of it, you don't need less of it. You need it to get it, and you certainly need it to get more of it. But if you already don't have any of it to begin with, you can't get any of it to get started, which means you don't really have any idea of how to get any of it in the first place, do you?

Only if there's a happy ending.