Hands down, ego is the true enemy of success.
Our ego is like a third party running a firewall deep in our brains to protect itself from everything it dislikes, letting in only what satisfies its own curious needs.
When your attention should be on your customers, the ego shines a light on itself.
A simple example of this is the decisions we make based solely on our own opinions.
Consider which decisions you have made recently, informed purely by your preference. Quite a few, I imagine.
It's not about us.
Successful business models do not fit into the black hole that is the ego.