The meaning of this sentence is that teenagers should not stay in unrealistic fantasies, but should have lofty aspirations and unswervingly move toward their own goals. Utopia refers to an idealized social state, which is often far from reality. Teenagers should understand that there are all kinds of challenges and difficulties in the real world, but they should keep their vision and pursuit for the future, have their own goals and ideals, and work hard for them. Only when a teenager is ambitious can he keep a clear head, not be stopped by difficulties, and move forward firmly towards his dreams. This sentence encourages teenagers not to be afraid of the limitations of reality, but to face challenges actively, pursue their own ideals and work hard for them.