Newborns come into this world believing that they are the center of it, because they really are the center of their own world. Then social conditioning kicks in, and they learn that the world is full of other people and that they are no better than anyone else. They are told not to consider only themselves, and since they are told this so many times, they end up putting themselves last; hence, their natural self-esteem is worn down day by day.
I've searched on oxfordlearnersdictionaries.com and find that "consider" means "to think about something carefully, especially in order to make a decision" or "o think of somebody/something in a particular way", but I think both meaning is not true meaning of "consider" in the sentence, so I guess "consider" mean "make a judgement", and "They are told not to consider only themselves" means "They are told judge only themselves", right? Can you help me to explain the meaning of it?