Ego is a double-edged sword. It's good to have one but it's equally important to be careful with it for it can cut you and leave you bloody.
Being egotistical can cause a lot of problems in your life. The first and most important of those problems is that it will earn you a lot of hatred of people around you, including your loved ones if you are not careful. See, no one really likes people who think they are special and that they are the only special people out there and therefore everyone else around them must run around pleasing them, no, nobody likes that. A little of ego is fine and people understand it but the moment you turn egotistical, you paint a bulls-eye on your back (you maybe lucky to even realize it) and it won't be long before people bring you back down to earth and make you smell the ground.
Another problem associated with being egotistical is that it makes you a target for other egotists who want a fight with you. All they will have to do is to trigger you by saying provocative thing to you so that you respond in a similarly provocative way or maybe even more which they would use as an excuse to get rattled themselves and start a fight. When you are egotistical, you are always an easy prey because people would just assume that you are reactive and easy to bait.
This is why ego control is a superpower. Unless you learn how to control your ego, you are always going to run into problems at some point soon. And not only will you rattle complete strangers or acquaintances, but worse, you will pick up the heat and hatred of even the people near and dear to you, including your family members, which is about the worst possible thing one can imagine. Therefore, it is necessary to learn to keep your ego in check. Though that certainly doesn't mean that you don't have an ego altogether.