In this task, you're given an article and an answer. Your task is to generate the question for the answer based on the given article.

Article: If You Make a Mistake, Don't Worry! Yeah, you'll want to forget about them, but mistakes can be useful. Making a mistake doesn't mean it's the end of the world. In real life you have to grow and mature, and with that comes some growing pains. You know you should have studied hard but you went out with some friends instead. You know you should have put the money into the bank for a rainy day instead of spending it on all kinds of things you didn't need. It's the growing pains called mistakes that most people make when they are growing up. Face them. You are going to make them. Learn from them. All of the people you wish to copy, such as all the experts in your business field, have made mistakes. They'll continue to make mistakes for all their successes. One of the major differences between people like them and the vast majority of others is that they don't let their mistakes stop them. Instead, they use their mistakes as learning tools. At the very least, when you make a mistake, you'll know what not to do. And you can help others by warning them of the mistakes you've made. Don't let mistakes stop you from doing anything. Learn from them, don't hide in a closet. Facing up to your mistakes now and later will mature. What mistakes are you making right now? Take a look at anything you might be doing wrong. Take a step back and evaluate your situation, then fix whatever needs to be corrected. Then move forward. Always remember your mistakes to remind yourself of what not to do for the future.
Answer: Because next time you know that money shouldn't be wasted.
Why does the writer say mistakes can be useful?