I'm done with school and just doing this for fun. I'm tired after my workout, but try to get good sleep and eat well. I drink caffeine to stay awake when I have to accomplish a task when I have to. I was never good with eating fruits and veggies, but lately have found smoothies to be an awesome way to get a quick digesting meal in. You don't want to say eat a burger and go spar. The smoothies give me good energy and recovery. I usually toss in vanilla yogurt, banana, frozen strawberries, spinach, and a good scoop of protein pow. I've been drinking 2 of these a day on top of 3 meals. Usually an hour before working out and right after. I'm typically running on adrenaline after my workouts so I'm not tired. Then I hit a wall.
Train with your limits in mind. I've been athletic all of my life, and the main thing I try to keep in mind is where the line is. If I play with the line too much, I get hurt. Smoothies (lol) and other things aside, do it for yourself. Addressing your question about getting used to the training... workout as your body allows. I'm the kind of person that's always trying to raise the bar, so if i'm not sore or tired, I feel like I didn't do enough.
I box because I'm masochistic and love the fast and intense workouts involved. I've never been so fit in my life. It's not a "oh I want a beach body" kinda thing. It's more satisfaction from the process... progress. I work with a tight community of good people. They are like family and keep me positive. What kind of program are you in? I'm not in any kind of formal boxing program, so I'm not forced to do anything. I just like it. If I wrench my shoulder or tweak my foot (both right now), I rest up and do other things. Sorry, I'm ADD and longwinded..
I like this video when I'm feeling lazy.
How Bad Do You Want It? Eric Thomas inspirational video - YouTube