Being a human today is complicated. Life can be challenging enough without having to go against the grain of our basic personality. Which is why it's important for us to do what we're best suited for. This applies to work, relationships, and even how we spend our free time.
Self knowledge allows us to do more of what we're good at, and, at least, develop strategies to counterbalance our weaknesses. But even more important, self-knowledge helps us navigate the moment-by-moment flow of life.