Lesson you understood too late?

[Opiate32]

I was thinking about how some advice doesn’t really make sense until life forces us to experience it ourselves. Looking back, there are things  once ignored that seem obvious now.

What is one lesson you wish you had understood much earlier? It could be money, work relationships, health or life in general.

Do you think people have to experience some lessons for themselves or can they truly learn from someone else’s advice?