So says Ryan Holiday about The Fight To Master 'Ego', our greatest opponent.
The Ego we see in play on a day to day basis goes by a more casual definition : an unhealthy belief in our own importance. Arrogance. Self-centered ambition.
It is that petulant child inside every person , the one that chooses getting his or her way over anything or anyone else. The need to be better than or more than with everything or anything...anyone or everyone. It is the sense of superiority and certainty that exceeds the bounds of confidence and talent.
In this way, Ego is the enemy of what you want and what you have...of mastering a craft...of creative insight...of working well with others...of building loyalty...of repeating and retaining ones success. Just your enemy all the way.
It repulses advantages and opportunities. It's a magnet for enemies and errors. Cyrillic Connolly rightly says - it sucks you down like the law of gravity.
Unfortunately, ego is easy to identify in others but difficult to identify in self, however obvious that may be.