The past of "withstand" is "withstood". Perhaps there's a clearer way of asking your question. What did you do the last time you were under stress? (asking about a specific event) What do you do when you're under stress? (asking a general question) What would you do if you were under stress? (asking a hypothetical question - note the verbs!)

Thank you for your help !

A mistake in case grammar . I mean "what did you do the last time you were under stress?"

I don't understand the question. Were you trying to ask 'What do you do to relieve stress'?