It means that the emotional experience is not deep enough. It’s a common poem that you don’t understand love when you’re young, but you’re at a loss when you understand it. It means that when you’re young, you don’t have a deep understanding and experience of feelings, love, etc., and only later do you realize that the choices you’ve made or the opportunities you’ve missed have made you regretful. People feel helpless and lost. It is a profound aphorism that reminds us to cherish the present, seize opportunities, and think more, experience more, and learn more when we are young, so as to avoid regrets and losses in the future.