On airplanes, they warn you that during loss of cabin pressure, you must first secure your own oxygen mask before those of others. (You can’t help them if you pass out). Similarly, you must support your mental and physical health before you can do the work of graduate school. OK, so maybe there will be a crunch time that requires a lapse in sleep, food, breaks, (friends, procreation, nutrition, exercise, vacation, romance, pets, movies . . . .). Hey! You can’t keep that up! And it doesn’t have to be that way!
Rescue yourself before you rescue your class paper, or dissertation, or . . .

You cannot continue to make the world a better place if you pass out, or drop out, along the way.