We usually hear the word egoist, or selfish, from others. They may call someone that to make him/her change the behavior. So, they kind of want the person to do what they wanted from him/her. Aren't they supporting their ego in this case ? lol
As you see, egoist is a person who wants to do the things his/her way. Of course, others should be considered as well. But ignoring your own freedom and giving it all to others is not the right thing to do. If something is shared among a few people and someone took a bit more because it's deserved, it shouldn't be called an egoism. Maybe that person knows that he/she will use it the proper way and the return will be higher for everyone.
I mean that there are situations where egoism could be useful. That's called healthy egoism. For example, if parents want to work and the child wants to play. The parents should be egoists and tell their kid that they have to work and that's a priority. So, if the parent didn't do in this situation what the kid wanted, it doesn't mean that the parent is selfish. It's a kind of controlled ego.
In psychology there are many negative aspects that should be considered positive sometimes because the priority maybe more important than ethics !
For example there is a healthy carelessness that could be also a form of egoism !