What is the main idea of this excerpt from “when you are old” by william butler yeats?

"When You Are Old" by William Butler Yeats is a poem by a speaker who reflects on a former lover he has lost. The poet tells the woman to think of all the men who have loved her in the past, and how most of them have loved her only because of her beauty, and other false reasons. Nevertheless, the speaker always loved her completely. He also tells her that he is sure she will regret how their love ended, as it was the best she ever had.