I need more stamina. help??!

I need more stamina. help??

i am a college student, and i love to work out. i like to do it 4-5 days a week. However, there is one problem; after a workout, i get exhausted. I like to work out a lot, but i don't want my grades to suffer. Therefore, I need a lot of stamina. I eat hell lotta food and get about 6 hours of sleep per day. I wanna be able to function well even when i only get 4-5 hours of sleep. How can i increase stamina?

Work out your abs and thighs. They are your stamina or what I would like to relate to in video games, "Your Health Points bar". The more muscle there is in your core the more "HP" you have. Start using the Captain's Chair. Go on it and lift your knees up to waist height. Then stretch your legs and lift your legs down. Repeat as many times as you can, Rest, and do it again. Also you can do bicycle kicks. You may look it up because It's hard to describe how to do it. Also get at least 8 hours of sleep. Also workout only 2-3 days a week. And do Aerobics on the rest of the days(such as jogging). On weekends you need to rest. Resting is "a warrior's best friend." ~ Shuriken School(lol) Good luck and have a great day.