From Longman Dictionary of Contemporary Englishthank your lucky starsthank your lucky starsspokenLUCKY used to tell someone that they are very lucky, especially because they have avoided an unpleasant or dangerous situation You should thank your lucky stars I got here when I did! → thank
Examples from the Corpus
thank your lucky stars• He was probably even now thanking his lucky stars for a narrow escape.• The Bruins this morning are thanking their lucky stars for goaltender Bill Ranford.• Thank your lucky stars the boy wasn't seriously hurt. 