Certain things happen to your brain and body when you are tired.
it makes you physically weaker (obvious but needs saying)
it makes you physically and mentally clumsier
it makes you less able to gain executive control of your mind and body
If you are tired, then you are likely to lose physical strength. This can start a vicious spiral:
loss of strength means you take longer to do things
taking longer to do things means you have less time to recover
less time to recover means you lose further physical strength
PHYSICAL AND MENTAL CLUMSINESS
Your mind and body rely on a wide network of support. When you undertake one action, although it seems narrowly-focused, there is always an enlistment of your whole body in some shape of form.
For example, you may think handwriting is a matter of just moving your hand. However, if you watch yourself carefully, you will eventually notice that your whole arm and shoulder are enlisted, as well as the rest of your body as a kind of subtle counterbalance to what your hand is doing.
In addition, mentally, you may think handwriting is simple. However, your mind, when writing, is engaged in several supporting activities, such as anticipatory and compensatory acceleration and deceleration, decisions about how much to elaborate or simplify, pressure decisions with regard to writing instrument and paper, and short term effort decisions based on the anticipated long term effort planned.
In any action, the same complex network of counterbalances is in place.
This explains why, when you are tired, you start to drop things, your actions become messy, and accidents happen more. This is not only physical, but also mental. It explains why, when you are tired, your memory tends to fail, your communication becomes less subtle and nuanced, and you fall into more arguments with others.
LOSS OF EXECUTIVE CONTROL
There is a subtly-balanced relationship between your conscious self and your automatic self. In normal life, there is a payoff between the two. For instance, when you are travelling, your conscious self makes decisions about where you are going, and your automatic self backs that up with automatic actions which support those conscious decisions.
But there is more than this. In a feedback loop, your conscious self then picks up what your automatic movements are doing, and corrects and compensates for what it observes.
Very roughly speaking:
Your automatic self operates by association. Thus, if the environment reminds your automatic system of something it usually does, then by association it will make guesses as to what it is supposed to do next.
Your conscious self operates by inhibition. Thus, if your conscious self senses something that doesn’t fit its model for correct living, then it will try to inhibit the parts of what it sees that it doesn’t like.
When you are tired, their relationship becomes painful to watch. Your conscious self sends you upstairs to get a jersey. Your automatic self then makes a bad guess at what is wanted, and cleans your teeth. Your conscious self, distracted by the teeth-cleaning, can’t remember what it came upstairs for anyway. Your automatic self, prompted by this idea of forgetting, starts off on a fearful thought-stream about losing your memory. Your conscious self notices the fearful feeling, and makes a wrong conclusion that there is something to fear in the outside world. Your automatic self then hears this reinforcing fear message, and seeks refuge in an automatic comfort activity, such as smoking, drinking, checking social media, or binge watching TV.
EFFECT ON ANXIETY
If you are already prone to anxiety or depression, then tiredness can make the loop of mental illness worse.
Anxiety is often characterised by a ‘felt lack of capacity’, a tension between what your conscious mind says should be done, and your self’s ability to do it. In the context of tiredness:
Increased physical weakness, and increased clumsiness, plainly inhibit your capacity, increasing anxiety if you insist on continuing to judge yourself.
Loss of executive control means that your automatic self goes off on more flights of fear and fancy, without your conscious mind being able to get a grip. You will have an increased sense that you are not in control of your life, and this will feed your anxiety.
In relation to tiredness, if you suffer from anxiety, I’d suggest a quick review of three aspects of your life:
Physical strength review – are you attending to three key things that bring physical strength: sleep, nutrition, and exercise? Are they your priority, or are you just assuming you will get round to them once you have done other things?
Timetable review – are you giving yourself sufficient time and space for each activity, so that it can be accomplished without a desperate sense of urgency? Who said that, to be efficient, you have to have this constant sense of burnout? What rubbish!
Seek refuge in controlled activity – bring your executive functions under control, and into harmony with your automatic functions, with smooth, disciplined activities such as yoga, meditation, crafts… just make sure the activity is a single one, and simple enough to bring order from chaos.
Tiredness brings loss of strength, clumsiness, and loss of control.
If you are already prone to anxiety, getting yourself tired can make it far worse in a kind of spiral.
If you are in that spiral, then a quick review can be helpful to make sure you have:
an easy timetable
simple, controlled activities