The Ancient Greek aphorism says, “Know thyself.” But it is very difficult for us to identify our fundamental essence or identity. Perhaps you have to back into knowing yourself through a process of elimination:
I have a body, but I am not my body.
I have possessions, but I am not my possessions.
I have roles in life, but I am not my roles.
I have a mind, but I am not my mind.
I have thoughts and feelings, but I am not my thoughts and feelings.
If you go far enough with this it seems you eventually get to… well, nothing! When you’re there, you are really close to identifying what you really are. It feels like “nothing” because your mind can’t comprehend it. But just because your mind can’t comprehend it doesn’t mean it’s “nothing.” It’s just something that your mind can’t fully comprehend.