personally, if i have a day off (hah, whatever THOSE are), i will go to the gym and work out super hard, but any other day, I have a really simple routine:
step 1: pick a simple exercise
step 2: do 10 reps
step 3: set a timer for an hour
step 4: repeat until you run out of day
on a good day (meaning i didnt sleep for 12 hours), i do about 140 push-ups, sit-ups, or squats a day, which is pretty decent for a workout, and the time in between each "set" is enough time for your muscles to basically repair themselves, so it isnt too strenuous.
I also eat 4 or 5 meals a day, but slightly smaller meals, so i'm eating the same amount, but spreading my nutrient intake more evenly.
also, i did martial arts for like 5 years, and am starting to get back into it. good fun