以下是一些：

1. Age is just a number.

2. Youthfulness is a state of mind.

3. You're only as old as you feel.

4. Age gracefully, but stay forever young at heart.

5. Embrace adventure and you'll stay young forever.

6. A youthful spirit keeps you forever young.

7. Don't let your age define you; stay young at heart and in mind.

8. Keep a positive attitude and you'll stay young forever.

9. Age only matters if you're a cheese or a wine.

10. Live life to the fullest and you'll be forever young.

这些句子表达了年龄仅仅是数字，要保持年轻需要一个积极的心态，可以适当冒险，保持年轻的精神等等。