lose sleep(redirected from lost sleep)
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To worry excessively about someone or something, perhaps to the point of literally being unable to sleep. Oh, those two argue all the time—it's nothing to lose sleep over. I hope you won't lose sleep over this issue with the printer. I'll call IT in the morning and see if they can fix it.
lose sleep over someone or somethingand lose sleep about someone or something
Fig. to worry about someone or something a lot, sometimes when one should be sleeping. (Often used with any and the negative.) Yes, Kelly is in a little bit of trouble, but I'm not going to lose any sleep over her. Don't lose any sleep over the matter. I refuse to lose sleep about it.
lose sleep over
Worry about, as in It's too bad the experiment failed, but I'm not going to lose sleep over it. This expression, often put negatively, alludes to actual insomnia caused by anxiety. [First half of 1900s]