keep one's counsel(to keep one's own business private; to be discreet, careful, or circumspect in what one says concerning one's own thoughts, deeds, or situation; to keep a secret for someone else КГА)
keep one's mouth shut(I don't have to tell you how important it is for you to keep your mouth shut about all this. • If she had kept her mouth shut she would still have her job now.)
hold on to one's hat(an expression warning someone of a big surprise. This expression may allude, according to lexicographer Eric Partridge, to a wild ride on a rollercoaster; Am.E.: Hold your hat – we just won the lotteryTaras)
