《当你老了》是爱尔兰诗人威廉·巴特勒·叶芝（William Butler Yeats）创作的一首经典爱情诗。这首诗以其深沉的情感和优美的语言，表达了诗人对爱人永恒的爱意与思念。以下是这首诗的原文：
When You Are Old
When you are old and grey and full of sleep,
And nodding by the fire, take down this book,
And slowly read, and dream of the soft look
Your eyes had once, and of their shadows deep;
How many loved your moments of gladness,
And loved your beauty with love false or true,
But one man loved the pilgrim Soul in you,
And loved the sorrows of your changing face;
And bending down beside the glowing bars,
Murmur, a little sadly, how Love fled
And paced upon the mountains overhead
And hid his face amid a crowd of stars.
这首诗通过想象未来的情景，描绘了诗人对爱人青春流逝后的深深怀念。诗中的“one man”指的是诗人自己，他不仅爱恋爱人的美貌，更珍视她内在的灵魂与变化中的忧伤。最后一节则暗示了爱情的消逝，但即便如此，这份情感依然纯净而美好，令人回味无穷。
《当你老了》以其真挚的感情和细腻的描写打动了无数读者，成为跨越时代的经典之作。它提醒我们珍惜当下，用心去感受生活中的每一份爱与温暖。