There are many things that only come to us with age. Learning lessons is a fact of life that we have no choice to accept. Still, that process of acceptance is rarely a quick or easy one. If there is any point to this ridiculous existence of ours, it's that we have to learn stuff. We often suffer from the preconception that we mostly do this as a kid, when we have to get all the obvious milestones out the way. However, many of the big emotional things come later.
Perhaps this makes it a fruitless exercise for people to share the realizations they had as they get older, because we will only ever internalize them when we're ready. Nonetheless, it can be nice to feel smug about getting a heads up. Also, not all of us learn the same lessons, and some don't learn anything. In a way, just going through the process of realization puts us one step ahead.