Some people are shocked at how a Torah observant Jew can overcome temptation while everyone is sitting in the hall- eating and drinking, and what? does he have no desire? does he not want to eat? he also wants to eat- he's also hungry like them, but he overcomes- so he'll eat a fruit or vegetable that he knows with complete certainty that there's no problem with it- (if anything he will set aside a tenth ) but he will not put himself even in a question of doubt of prohibition - if it's not one hundred percent and completely smooth to the extent that is known to him. but this is the explanation, that a person who understands the significance of a fear of prohibition- that's it's like poison- so he relates to it differently. 