There are many , many sleep expressions in English . But today we talk about ones that deal with problem solving . Now , it is common to sleep on a bed . When we go camping , we sleep on the ground , or we sleep on a cot . If we fall asleep watching television or when we visit a friend's house , we may sleep on a couch . And sometimes we may have to sleep on a floor . But “to sleep on ” has another meaning . If I have a problem and cannot think of an answer , I can “sleep on it .” Often an answer comes to me the next day . Let's say some co-workers are working on a project together , and they run into a difficult problem . No one can think of a way to solve it . One person might say , “Look , we're not getting anywhere . So , let's sleep on it . Tomorrow we can try to figure this out .” To “sleep on " something means you give yourself time to think about a problem overnight . You plan to make a decision about it later . This does not have to mean that you are actively thinking about the problem . Your subconscious may be working on it . For example , if I am writing a story and run into a problem , I often sleep on it . I think about the problem before I go to sleep and hope that my sleeping self comes to the rescue ! Sometimes we use this expression when we just want more time to pass . We also use it when we want to look at a problem with a rested mind . We know that sleep is necessary to be healthy , both mentally and physically . Sometimes a problem doesn't look so bad the next day after a good night's sleep . Here is another sleep expression . Some problems are not a big deal — they are not important . You can describe them as “nothing to lose sleep over .” And if you want to say you are not going to worry about something , you can say you're “not going to lose sleep over it .” Let's listen while two friends use this expression . Hey Tish , did you hear about the new apartment building coming to our neighborhood ? It's going to have 100 units ! Why do you ask ? It will mean a lot MORE people and a lot LESS parking . Aren't you upset ? Well Mark , we DO live in a city . And cities have lots of people . So , I'm not losing any sleep over it -- if that's what you're asking . Good for you . I've lost A LOT of sleep over it . Okay , who is upset by the new apartment building – Mark or Tish ? If you “sleep with one eye open ,” you are too distrustful to fall asleep . You are suspicious of others around you . You are worried or even fearful that someone or something will hurt you in your sleep . For example , once I took a friend camping with me . She was a city girl and had never been camping . While sleeping in a tent in in the woods , she heard animal sounds and movements in the woods all night . In the morning , I asked her how she slept . She said , “I didn't sleep a wink . I slept with one eye open the whole night !” If you run into a problem with English , try sleeping on it ! Maybe the answer will come to you with the morning sun .