Why is it important to know yourself? Well, we can only love that, which we understand and know. Part of knowing yourself is knowing what you want and what you need, then ask for it.
You cannot get what you want and what you need if you don’t ask for it. (except by chance, rarely, sometimes).
Knowing yourself also helps with boundaries. If you don't know who you are, where you begin and end, and where the other person begins and ends, how are you going to set boundaries?
Knowing yourself is important for your happiness.
In order to be happy, you have to know what brings you joy and what brings you sorrow, what contributes to your wellbeing and what is detrimental to it.
Knowing yourself shapes up the choices that you make. When you know yourself, your choices become conscious. And you can never make a mistake when you make a choice consciously.
You always make the right choice when your choices are conscious. You make better choices when you know yourself, because you make choices that serve your wellbeing.
It’s the unconscious choices that hurt us.