Lyric discussion by philmud 

I think this is really pretty- obviously about a breakup, or an impending breakup- he's thinking about a fight, or some unkind things he said and he knows that it signifies the end of the relationship. Possibly she's still asleep after this big fight and he knows that when she wakes up they'll split, so he's telling her not to wake up because it will save her that pain.

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