我明白，你是不能一辈子陪着我的人，你始终有一天会走，我不再会要求你留下了。

I understand, you are not a lifetime with me, you always one day would go, I no longer will ask you to leave.

youdao

我只要求你，对我说一句真诚的话，一句一辈子只能说一遍的话，一句只有我才明白的话。

I only ask you, say to me a sincere words, a lifetime can only say it again, only I didn't understand.

youdao

我也明白两个人在一起谁也不能保证谁就是一辈子。

I know there's no guarantee of being together forever.

youdao