Whatever you think you are -- you are more than that; whatever and however you identify yourself, you are far more than that. The problems with identification are many -- whether it is identification with/ as your gender, your nationality, your sexual orientation, your finances, your social reputation, your career, your role as a mother/father, your political affiliations, you religious beliefs, your competence or skill in a certain context, etc. -- to identify with any of those things will create problems if/when they are taken away or are shaken at their foundations as you will experience a very real identity crisis. But the "why" it creates problems is because it is not really who you are -- and to identify with it is *at least* selling yourself short.
In the face of such a crisis there are only two directions to move from an ego perspective -- expansion/evolution or contraction/regression. There is no neutral. You can expand to incorporate the new information/circumstances, or you can dig in, regress, and solidify (which requires engaging in some degree of self-deception).
Who you are is none of that. Who you are is Spirit. If you want to identify with something, identify with yourself as Spirit.
Which every breath - breath out your lack of self worth that has you play small and identify with something less than your full birthright and breathe in the fact that who you are is ... all of it.
Who you are is the Witness.