acho que é a melhor expressão

é melhor se calar antes que você diga alguma besteira/fale algo de que se arrependa

http://www.phrases.org.uk/bulletin_board/49/messages/313.htm...

In English there is a common expres-sion "He put his foot in it" which is used to describe someone who has tactlessly or accidently said something that embarrasses, offends or upsets someone. (I think the"it" is cow manure in the literal meaning of the phrase). Sometimes the phrase is varied to become "he put his big foot in it" to emphasise the ineptness of the person making the remark (a big - and therefore clumsy - foot is more likely to find itself in the wrong place than a small one). If the Englishman hadn't predicted the offence that his comment caused to the main character (or the degree of offence had been greater than intended by the joke), then "There wasn't wool enough in the basket to knit socks for those feet" means "he has big feet" which suggests "and he stuck his big foot in it" (to my mind at least). As I said, perhaps if you quote some more of the text it might give more clues. Pamela

Julgo que é este o sentido: cometer erros, dizer asneiras (algo errado), etc.

Em Portugal, diríamos "é melhor calares-te antes que metas a pata na poça" ou "antes que metas os pés pelas mãos"

Em português do Brasil, talvez "pisar na bola", "cometer uma gafe", algo assim. Veja também este link de outra referência idêntica no ProZ:
http://www.proz.com/kudoz/english_to_portuguese/other/286283...

uma possibilidade

Mais uma sugestão.

HIH

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Note added at 6 hrs (2012-01-06 19:28:27 GMT)
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Estamos aqui para ajudar. Um abraço.