When saying this quote, Lucius Annaeus Seneca was saying that events that can lead to wisdom may come by chance, but to gain wisdom from the situation requires effort and intentionality.
Wisdom just doesn’t come through what we go through. We have to want to learn from it. When these things happen, we have to ask the universe, what you are trying to teach me? What do I need to learn?
Say you are walking down a dirt road and there is a huge pothole over the hill that you didn’t see immediately. You fall into it and twist your ankle. Your ankle hurts, but you get back up, dust off and continue on your way without giving thought to what may lie ahead.
A wise man experiences the same thing, but instead of just continuing ahead, mindlessly, he considers what he just experienced and tells himself there might be some potholes down this road that cannot be easily seen. This man will proceed with a measure of caution, knowing that something may be up ahead. You will encounter all kinds of experiences in life. And each experience can teach you something, if you want to learn.
