Society, or the world or the Universe, call it whatever you want, will reward you in direct proportion to the value you give to them, not to yourself. It does not care about you, it cares about itself.
On the other hand you should never forget your needs as a human being while working. Focusing too much on others, becoming in practice a slave, not eating well, not sleeping well, not having fun, will only burn you in the medium and short term.
That will for sure make you not to contribute much to others on the long term.
The advice is given by people that had overextended themselves and experienced the burnout in their life. They compare themselves to others and it becomes obvious that some people are doing exactly what they love to do.
They assume that this has always been the case. Usually it is not. For example my father met a man called Carlos Sainz, a car driver that won some Dakar, when people see this man succeed, they assume it was always easy to him. They can't see the effort and sacrifice that led to him winning races.
I fortuitously met Rafael Nadal, a Spanish tennis player. People see him winning titles and believe that is his life, but his life is 90% training training and training(repeating repeating repeating) to a level that will bore to tears any normal human being.
I like playing tennis myself but it will be impossible for me to spend my life doing that.