There are some people who think that the worst thing one can be is selfish, and there are others who think that only self-interest is real and that collective benefit is a ruse.
In fact the world consists of self and others, and benefiting the world means benefiting other people and oneself.
Certainly there are times when the collective benefit really is a ruse. Under the Soviet Union, people were told to sacrifice themselves for the greater good, only to find the fruits of their labor wind up in Swiss bank accounts of the bureaucrats. There are other altruistic efforts however that are not a ruse at all. I am involved with the Salvation Army, and there is nothing corrupt or tyrannical about that organization.
With selfishness, most times the accusations are wrong. In a Russian film “Bolshoi,” the mother of a ballerina tells her that she is selfish. No; she was a star. What she did brought fame and pride to the family, which she would not have accomplished if she had pursued a more conventional career. I have been told that my translations of Russian poetry are well known in Europe, which means that by doing them I am doing more for my family than I would have if I had stayed in the computer industry. I also put in a vast intellectual effort into addressing concerns of many people other than myself. So when people accuse me of being selfish or self-centered, they are wrong.
Once again, the world consists of both self and others, which means that neither self-interest nor altruism are wrong. They have to be done the right way. Altruism should not be used as a cover for tyranny and corruption, and self-interest should not be used as a cover for carelessness and short-sightedness. Both are inextricable from human design, and both are legitimate. They have to be done the right way.
Do not just benefit yourself, and do not just benefit others. Benefit both. That way you are addressing the totality of the world with your actions, and you stand to genuinely benefit everyone you stand to affect.