Much has been written about the ego, most of which is negative. This is accurate because it is the power of the ego, depending on its health, that can be the catalyst for the quality of many of our decisions and behaviours.
A healthy ego is one where good self-esteem reigns.
What this means is that there are little to no insecurities about one's real feelings of worth so there would be little reactivity when the outside world challenges one. A healthy ego does not have to negatively react, defend, justify, rationalize, fight, manipulate or hide from challenges because it is convinced that whatever is going on outside will not change who one is and what one stands for.