"He is on the path of life who heeds instruction, but he who ignores reproof goes astray"
This is the Hebrew word musar, which means discipline, chastening, correction, reproof, punishment, instruction. These often-indicated hard lessons; ones that were not easy to absorb. There is clearly new information here, but it comes in the form of a setback or something done wrong that could have been done differently.
Solomon is trying to get us to pay attention to what happens to us and see it is as a lesson. He wants us to realize that God does not waste our experiences but wants us to learn from what we go through.
What are the things right now that are not going the way you want them to go? These areas are the prime candidates for this kind of instruction that Solomon wants you to pay attention to in this verse. What could have been done differently? What choices could have been made so that this negative result could have been turned to a positive result? What have you learned from this situation? If you do not learn from these types of things, then you are largely condemned to repeat them.
This is the Hebrew word azab, which means to leave, forsake, let loose, abandon. All these carry the idea of ignore which is the word that the translators used here. The good is contrasted with the bad. Both people have negative consequences happen to them when they mess up or don't calculate correctly, but the person who is on the path to a great life pays attention to why it might have happened, other ways of handling it, and choices that could have been made differently to minimize or eliminate the problems.
The fool here just lets the rebukes of life come and go in their life with little evaluation. That is just the way life is to them. They just accept rebuke, difficulty, and problems as the fare for living. The idea of God engineering consequences into the society doesn't fully enter their thinking. If it does, they wonder why would God have wanted anything bad to happen to them.
God has made the rules for life, and we would do well to pay attention to them.