I still remember trying to help my Russian friend, Dmitry, understand the slang term "bummer". He spent a lot of time hanging around us Americans and I suspect part of it was to glean some American idioms from us. In Moscow the English that is taught is purely British (they live in "flats" and take the "lift" to get to them, among other things). At some point though, he'd heard someone use the word bummer, but didn't get it's meaning, so he pressed me.
I don't remember quite how I answered him then, but if he were here today I might answer something like this:
Bummer: getting a rejection letter from a magazine that you submitted to six months ago? No, that's good news. It means you mattered enough to get a response.
Bummer: losing your glasses/sunglasses (again!)? Sort of, but not so much so if your vision coverage allows for a new pair this year (phew!).
Bummer: forgetting to thaw the meatloaf for dinner and resorting to chicken patty sandwiches instead? Naw. The meatloaf can wait.
Being this guy today?
Now THAT'S a bummer!