用：一种说某人已上一r年纪的婉转说法二
意：你可不像以前年轻啦!你毕竟上了年纪了
例：Come on , Frank! Don't do that-you're not as young as you used to be.
喂，弗兰克!不要做那种事了—你可不是什么年轻人啦!
you've only yong once.
用;来鼓励自己或他人珍惜青春年华、多做些年轻人该做的事。青春短暂啊，
例.t think you'd better have a goad time before you settle down-remember you're only young once?
我看安定下来之前你真该好好玩玩，别忘了，青春短暂易逝啊!
