the young at heart

例句：

1. 1. He's always been known for his youthful energy.
   他以年轻活力而闻名。
2. 2. The old man is full of life and has a young at heart.
   这位老人充满活力，心态年轻。
3. 3. She was always the youngest in her class, but she never seemed to have a young atheart.
   她总是班上最年轻的，但她似乎从未有过年轻的心态。