Sense of self.
Ultimately everything depends on from where we derive our sense of self. It could be from our culture, religion, political affiliation, nationality, our dress, new hair style and all things external to us - the world of forms. Or it could be from deep within, from our very existence or the feeling of I. In this case, our sense of self is not actually derived from an external entity but it is the feeling of being or completely present. Even the thought can be considered as something external since its away from the feeling of being. Ego is nothing but the derivation of the sense of self from anything away from the complete presence. Being in thought is being in ego. There is nothing wrong to be in ego (we will be forced to) but we will just miss the wonderful feeling of being present, of being alive.
