Ego is a process
On p. 39-40 of my copy of In Love with the World, by Yongey Mingyur Rinpoche:
The term ego – or ego-self – is frequently used to describe the self-centered, fabricated outer layer of self, and we often speak of letting go of the ego, or dissolving it, or transcending it.
I myself had thought of adding wood to the fire [seeking out increasingly difficult situations to test out the limits of one's practice] as an ego-suicide mission.
However, the common usage of ego, both within Buddhist teachings and in the world at large, makes ego sound like an entity that has a shape and a size, and that can be extracted like a tooth.
It doesn't work that way.
Ego is not an object; it's more like a process that follows through on the proclivity for grasping, and for holding on to fixed ideas and identities. What we call ego is really an ever-changing perception, and although it is central to our narrative story, it is not a thing. It therefore cannot really die, and cannot be killed or transcended.
This tendency for grasping arises when we misperceive the constant flow of our body and mind and mistake it for a solid, unchanging self. We do not need to get rid of the ego – this unchanging, solid, and unhealthy sense of self, because it never existed in the first place.
The key point is that there is no ego to kill.
It is the belief in an enduring, nonchanging self that dies. The term ego can still provide a useful reference; but we need to be careful not to set ourselves up for battling something that is not there. Ironically, when we go into combat with the ego, we strengthen the illusions of self, making our efforts to awaken counterproductive.
Because ego is frequently identified in negative terms, especially among Buddhists, my father made a point of reminding me that we also have a healthy ego – or a healthy sense of self. This relates to aspects of self that intuitively know right from wrong, that can discern between protection and harm, that instinctively know what is virtuous and wholesome.
We trip ourselves up only when we become attached to these basic instincts and create inflated stories about them. For example, I had used ego in a positive way to explore, and then maintain, monastic discipline. But if I were to think, Oh, I am such a pure monk, I maintain my vows so perfectly, then I would be in trouble.