One important life lesson that you must never forget is that children don't really think before they act. They can be very insensitive and obnoxious. They'll endanger not only themselves but also others.
But you've got to remember that most of the time it's because they aren't really thinking about the long term consequences.
Imagine you were babysitting a kid and bought him a meal worth $10. Later that day he might tell his parents he only got a tiny burger off the dollar menue. At that moment in time he isn't thinking about how that would ruin your reputation, but how his parents will spoil him if they think he was starved. Of he course he could also just be evil, but that's a but more uncommon.
You just got to remember that a child doesn't really think before he/she acts. Try to give everyone the benefit of the doubt and you'll realize that it'll positively affect your mentality.