In codependent relationships you USE the other person to give you a sense of self. Without them you feel you cease to exist; you lose your identity and grieve for your lost self. You might use your job, role, or any behaviours or even substances to give you a sense of self; you use them as props and feel lost when you lose them.
Once you had a sense of self, but you lost it when the circumstances you were born into and the people around you didn’t acknowledge, recognize and mirror that self.
In relationships you search for others to mirror you. They never get it exactly right. As an adult, you can choose your own environment and the people with whom you wish to surround yourself. You can align your life with your self and live your truth. You can grieve your original loss of self and reclaim that self now.