A) Concentrate on your diet not only before the gym but throughout the day.l If you eat proper balanced meals throughout the day it will help the next day with your workouts. it keeps your body running properly. Also eat something in the morning to keep you going, you need the food in your stomach or else you may do more harm then help. I use to either eat a full breakfast (eggs, oats, veggies, fruit) or just a simple whey shake with oatmeal and some fruit. Whey is lighter then eggs so I can workout without a fulls stomach.
B) Proper rest is very important. If you are not getting enough sleep you may start strong but die out quick. Some times if you get up a little bit earlier then when you go to the gym it is better, you are more awake and can concentrate more rather then rolling out of bed and lifting. Also don't go into the gym thinking "Oh man I'm gonna die after this set I know it" if you do this you will def die out. Just get pumped and hold that energy the whole time your in there, don't let your mind get you tired before your body is. Get some music you can move to and LIFT!!!
C) Maybe change your routine/rep range. If you are lifting to failure every day it will take a toll on you. Try and vary your rep ranges. Higher reps lighter weight/higher weight lower rep. Pick a weight you can handle and don't go to failure every set. One week go real heavy with low reps 4-6 and go to failure only on last sets then maybe the next week switch to a 8-12 rep range and don't go to failure. Drop sets, super set, and going to failure are great but should only be used to change things up and keep your body guessing they should not be used as a staple in your routine.
D) As for supps you could try creatine, EC stack, and any of the numerous drinks (prince uses one that is suppose to be good, so I hear). When I'm feeling sluggish i sometimes pop my EC stack rite before the gym and it keeps me goin strong the whole time. But the one thing that keeps me going the most is determination and desire. Lifting is not a chore for me its the best damn part of the day. So when I go in to the gym I mean buisness and go full force, I am doing it for myself and give my full effort to do it rite and powerfull the entire time I'm in there. If you are goin in b/c you have to its tuff but you need to make due and put all your effort into finding, harnessing, and controling your inner energy and using it the entire time you int he gym.
Hey if the mornign workouts are tuff and you have ther ability to change the times you can go in try that also, it works for me. Different crowd in the gym and such may motivate you a little more as well. Hope some of these tips we gave you help out, G' Luck