Recently I was wondering how you would teach kids how to deal with money if there is no money you can see. There is a lot of research about the effects of seeing the money you spend and how this helps to assess how much you are actually spending. (No, your Spreadsheets don't help really.)

So if you don't learn this (to me one of the strongest and still most important) lesson as a kid, which effect will it have on your spending behavior in the long term?