There are too many expressions/idioms/phrases to mention! Some come from other languages; for example "carpe diem" ("seize the day" or "don't let life pass you by") is Latin and "c'est la vie" ("that's life" / "such is life") is French. Here are three I use a lot, which doesn't mean they are the ones which most English speaking people use! 1) "When there's a will, there's a way": If you really want to do something, you can. 2) "It's raining cats and dogs": It's raining a lot. 3) "Once bitten, twice shy": you can be frightened to do something a second time because the first time was unsuccessful. Some of these expressions are so famous that English speakers will just use their beginnings to make themselves understood. Sometimes I just say "when there's a will..." or "once bitten..." and the people I'm talking with understand me.