To be at peace, it is essential to know who you are, because you are who you are. You have always been you and you will never be anything but you. Nothing you do or think will change who you are. What you do and think though, can make you more at peace with yourself.
If you are not at peace with yourself, then you are missing who you are. You are likely thinking of characteristics, skills or possessions that you lack and would like to have, or have and would like to lack. You may be imagining relationships you would like to have, or relationships that you have but wish you didn’t. Those things are not who you are. Those are all circumstances.
Who you are is much more fundamental than what you do, what you have, or the people around you. Who you are is beyond any characteristics or credentials that you associate with yourself. When you know who you are, you will be at peace with yourself. It is possible to be at peace with yourself regardless of your circumstances. When you know your essence, you will know peace.