You shouldn't feel like crap after doing leg work. Perhaps you were coming down with something that was compromising your workout...like a virus.
No, no virsus. You don't get a virus training legs or training anything. And if I was coming down with anything I would feel it before I get to the gym. I know when I'm starting to get sick. I came into the gym eager and anxious to blast. When you take a set, especially for a large muscle group like legs, to positive failure. Meaning you can't eek out another rep to save your life, then you do a few forced reps, then rest pauses where you lock out, take three deep breaths and bang out another forced rep, do that for four more reps, with every rep lowered in a slow, deliberate fashion so that it burns going down, then immediately grab a 45lb plate holding it between your legs for wide leg Sumo-type squats for another 15 reps, then do some bodyweight squats until your ready to drop to the floor --- for the first set. Then leg curls again with forced reps, rest pause, burns. Then a superset of extensions and leg press in the same fashion with the Sumo squats and bodyweight squats, followed by a set of stiff leg deads -- then it was probably more overexertion then a virus. I'm almost sixty goddamn years old now!
I feel much, much better now from just lying on the couch for a couple of hours to give my body a chance to normalize. I was thinking if maybe this was how Sergio Oliva felt after Arthur Jones' put him through his infamous quad routine which consisted of one set of leg press, followed immediately by one set of leg extension, then heading straight to the squat rack. Every set done to the death under Jones' watchful and demanding eye. Witnesses said that after finishing up with squats Sergio fell to the floor and didn't move for twenty minutes. Sergio claimed he was in his biggest and best shape training under Jones in Deland, Florida.
Anyway, I got my appetite back and had some chicken, rice, steamed vegetables (broccoli, cauliflower and carrots) and three oatmeal raisin cookies. I'm now in that pleasantly fatigued relaxed mode and already drifting off to sleep.
Two days of loafing and recovering and I'll be back Friday ready to go full on HIT Arthur Jones' style for chest, back, and shoulders.