I was trying a JLPT mock test and there was a question in which you had to pick the sentence in which the given word was used correctly. In one of those, the given word was だらしない, and the answer was the sentence 「そんなことで落ち込むなんて、だらしない奴だ」.
But how can be だらしない be used to reproach an involuntary action? だらしない is commonly translated as "slovenly, lazy, untidy, undisciplined", and I don't see how that would apply to the action of feeling sad. Is there a problem with the translation? Does だらしない have a broader meaning?