There is lots of research showing that fatigue impairs cognitive function. This is why the military has “boot camp” to make certain behaviours and decisions almost instinctual so they can be done even when fatigued, because war means you sometimes have to work when you are under-functioning cognitively.
You are not fighting a war. You earn your living using your higher cognitive functions.
Make rest a priority
Rest may not be your highest priority but it should be right up there with research/writing and being a good teacher. You are not going to be a good researcher or teacher if you are exhausted.
I know it feels impossible, but the work you do when you are rested is more efficient and more effective. The transition from working fatigued to working rested may feel underproductive but it will result in better work later.
Rest is an even higher priority during illness and early parenting
If you have very young children, you are probably not getting good sleep. It comes with the territory. Being more conscious about making it a priority will enable you to be as rested as possible in the circumstances. “Mommy brain” is a thing, but it’s mostly just a special case of sleep deprivation impairing cognitive function.
If you are ill, even with a cold, you need energy to fight the illness. The illness may also be affecting your normal sleep patterns. It is not “giving in” to get more rest or switch to more restful activities during this time. Although you are entitled to sick leave, universities are very badly set up for actually enabling sick leave especially in terms of teaching. You may need to prioritize teaching as well as rest, but that means everything else becomes low priority until you are well.
For longer term or more serious illnesses, take the leave your medical professional recommends. A client of mine argued with her doctor to allow her to return to work 2 weeks earlier than recommended after a serious surgery because that would be the beginning of term. She got her worst evaluations ever that term, which made her realize that she was performing at well below her usual standard. Her cognitive function was impaired enough that she hadn’t even noticed as she was going along. You do not have to replicate this experiment. Your doctor is not making up those recovery time recommendations. Someone else can teach that class.
Make sure your fatigue is not caused by a treatable condition
I have heard a lot of stories about people finally realizing that their exhaustion wasn’t just that they were working too hard. If you are tired all the time, talk to your doctor about it. There are numerous possibilities including vitamin deficiencies (B12, D), other nutritional deficiencies like anemia, thyroid malfunction, sleep apnea, and probably a bunch of others. I’m not a doctor. You are not a doctor. (Or, at least, not that kind of doctor.) Google is not a doctor. Go see a medical professional. Here are some basic self-help tips about sleep hygiene and insomnia from the NHS.
Some of the things on that list also signal the importance of eating well. You may have nutritional deficiencies that require more than a change of diet or signal a deeper problem absorbing certain nutrients. But it can’t hurt to give higher priority to eating well, too.
Go to Bed: Sleep Debt and Sleep Deceit by Jason Jones on ProfHacker (includes further helpful links)
What does Reading Week mean for you? Reading Week (or Spring Break) can provide an opportunity to address fatigue.
Write all the things is not a summer plan addresses the need to incorporate rest into your plans for non-teaching terms
ADHD and sleep problems from ADDitude
Edited March 29, 2016.