Indeed we shouldn't get discouraged no matter the mistakes we make or how many times we fail. No one ever got better without having to fall. When we take a dip or fall, we should rise up, that we get better and conquer mistakes that previous put up down. Mistakes helps us get wiser has experience teaches us all things. The wisest are not those who have never experienced failures but those who chose to learn from. Every mistakes begets a learning process. That is why mistakes or failures are part of path to success.
For people who don't want to make mistakes. They are simply not ready to grow or develop as there is no way to achieve greatness or success with passing through this normal life pattern and principle. So to buttress or to prove your point, it is not possible not to ever make a mistake. It is a needed path to follow.
Interesting story about that tortoise. That is exactly the right mentality we should all cultivate if we intend to achieve much in our journey of life. We should all see the positives, that is what we gain from it all. We can't learn from something we know. Learning comes from experience that we face our encounter. Sometimes other people mistakes is a great learning point has we don't get to repeat similar scenario or situation.