Lack of Sleep Directly Causes Higher Levels of Stress
You know as well as I do that situations come up. Mistakes are made, something takes far longer than anybody could have foreseen and deadlines are run over. With stress levels already running high, adding to that stress is always a bad idea.
Yet a lack of sleep increases cortisol levels in our brains. Cortisol is the stress hormone, and higher levels leave you permanently in the fight or flight response, making you edgy, anxious and unable to focus. This lack of sleep and increased level of stress can also shrink blood vessels in the brain and lessen blood flow, which slowly starves your brain of nutrients and oxygen and leaves your mind feeling slow and muddy.
Lack of sleep affects focus
It's shown that being tired directly impacts your ability to pay attention to the world around you, with tests showing that our ability to filter out extraneous information, as well as focus on the important for long periods, are hugely impaired when you've had as little as one bad night's sleep.
Lack of sleep impairs decision-making
When you're making decisions, you need to be able to make them with a clear head and consider the current situation logically, taking into account all the evidence available to you, so you can come to the most intelligent, reasoned conclusion possible.
But studies show that sleep actually affects the mind in the same sort of way as being drunk. Ask yourself, would you make big decisions whilst inebriated? Of course you wouldn't. But somehow the idea of toughing out being tired and working through it is lauded. Even though they're having precisely the same effect.
More insidiously, over time your brain becomes acclimated to a lack of sleep, fighting off the fatigue and fuzzy thinking that comes with tiredness. Thing is, even though you feel well rested, there's a high probability your mind is still suffering. In all likelihood, you're still going to be unfocused and making bad decisions, but your mind will try to hide all of that from you.
And considering the cost of a single bad decision when you do what we do, that's a risk that you just can't afford to take.