Being identified with the ego is a good thing, we need that in order to function in our illusion of separateness, which we always return to while we're alive. But, not understanding there is anything beyond that can indeed be a bad thing. The result of experiencing an ego death/ego dissolution (my preferred term for it) should not be to suddenly begin identifying the ego as a bad thing and seeking to suppress it at all times. it should be to live one's life as a being with an ego, while understanding that the ego itself is an illusion. This does not diminish its importance or realness to us, but it does help us to look past it when appropriate/necessary.
Our ego is what makes us unique, it's the whole point of this existence in which we experience ourselves as separate from everything else. It's not a bad thing. It's just how it is.