Legs should be the bulk of your entire week,compared to any other day. If you can't go extremely hard on leg days then the rest is moot.
You name it I've done it(except vomit);light headed,collapsed on stairs leaving the gym,had legs lock on me when I'm down low half way through the squat,shaken violently from getting that extra rep or two out at the end,I turn pure red on the last set on the last few reps.
Even in the middle of winter when I throw in a pizza here and there,and take a day or two off during the week to change it up. I ALWAYS have a leg day,doesn't matter. Even after having sex twice within a hour. If you can't 'get in the zone' for leg days you won't have the heart and dedication it takes to shape the rest of your body.