It is not one or the other, but both. Yes, we can learn by trial and error. Personal experience is highly impactful and useful. We can also learn by analyzing the actions that other people make. We don't necessarily have to repeat the same errors in order to gain valuable insights. For example, you don't have to become an addict to know the devastating impact of substance abuse. All you have to do is to drive down the street where junkies shoot up drugs in broad daylight. That's what I meant by saying it is much less costly, because the price is too high to pay to learn this kind of lesson. By no mean am I implying that you should avoid taking risks or failures. Making mistakes is an important part of the learning process. Practice makes perfect through repetition and muscle memories, but practice making perfect mistakes also makes you an expert in failing. Parents who chastise their children when they make mistakes may not realize the enormous harm they are causing. Doing so makes children afraid to take risks, instills self-doubt, and anger. Instead, parents should give their children encouragement and discuss ways they can improve their chance of success the next time. No shouting. No demeaning. Just guidance. That is what some commentors misunderstood about what I said.