"This is probably the biggest pet peeve of the chronically ill: the suggestion that they should just suck it up and push through it. That is actually the worst single piece of advice you could give a chronically ill person, and this is why. People possessing average energy stores and bodies that aren't falling apart can go for a day or week or even month where they're not getting enough sleep. Sure they'll feel crappy, but once they take a weekend to really rest, their body will be back to normal. For a healthy person, it might be totally reasonable to push through some tiredness to get extra work done.
"Not so for chronically ill people. Being chronically ill is sort of like starting every day on three hours of sleep, regardless of how much sleep you've actually gotten. Strike that. It's like starting the day on three hours of sleep plus you have the flu. A flu that might never go away or get better. (I'm a bundle of laughs at parties, let me tell you.) If a chronically ill person tries to 'push through' their fatigue, they could actually make themselves substantively sicker. The immune system that was just sort of nibbling on their kidneys will now go on full attack, or the moderate pain they had in their joints will be turned up to eleven. And, as you can imagine, that increase of symptoms doesn't just last during the period that they're 'pushing through' their fatigue. It can last for weeks because now they've actually made themselves sicker. Telling a chronically ill person to just suck it up and push through the fatigue is like telling a lung cancer patient to just have another five cigarettes. Go ahead! Suck that smoke through your throat hole. It won't hurt you."
-- Katie Ernst, "Five Reasons Fatigue Isn't Like Normal Tiredness (Proving Most People Don't Get It)", 2016-03-24