the problem with the drains once and for all . This is how the expression is used in one of our stories: The team hopes to capture the cat on film, solving the mystery once and for all , but if they don't ? once bitten twice shy To be once bitten twice shy is to be very careful about letting something bad happen that has already happened to you once. When it comes to gambling, I'm once bitten twice shy . This is how the expression is used in one of our stories: I mean, an experience like that just makes you once bitten twice shy . once in a blue moon Something that happens once in a blue moon happens very rarely. I travel overseas once in a blue moon . one step ahead To be one step ahead is to have a small advantage in a competitive situation. We have to keep one step ahead of the competition or we will lose business. This is how the expression is used in one of our stories: For the time being credit card companies and banks around the world are turning to so-called smart cards in an effort to keep at least one step ahead of the scammers. one step further to a more advanced level You should take your English one step further . open a can of worms To open a can of worms is to reveal something unpleasant or something that will cause a lot of