explain sentence

Those are two sentences. The thought which they convey is meant to be ironic. There has long been a general belief that in order for a person to write great poetry -- or, indeed, create any great art -- that person must have "suffered". i.e. had some painful experiences which can then be translated into art. The writer of those two sentences is saying that everyone who has reached maturity has experienced adolescence and has, therefore, suffered. The teen-age years are seen as a time of universally painful experiences. As I said, the dictum is meant to be ironic.