When we sleep deeply, everything becomes history.

当我们沉睡时，一切都成为历史。

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We sleep more deeply when we are young, because we have a high metabolic rate that is greatly reduced during sleep, but also because there are people to protect us.

我们在年少时睡得更深，这是因为当时我们有很高的代谢速率，而睡眠能大大降低之。但同样也因为有人可以保护我们。

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