The concept of decision fatigue gained popularity in 2011 with an article in the New York Times Magazine. Essentially, our willpower decreases throughout the day as we make all sorts of large and small decisions. Lifehacker did a good job of summing it up at the time:
Each decision you make and the more choices you make throughout the day, the harder it gets for your brain to continue to make decisions. The result is that towards the end of the day when you’re low on mental energy, you’re more likely to either give in to impulses or avoid making decisions altogether. The worst part is that, often, none of us are aware of how mentally tired we are just from all the little or big choices we make throughout the day.
This 100% applies to me, especially when it comes to work. I do my best work in the morning. From there it tails off pretty linearly: I can usually get a pretty good block of productivity in the afternoon, but by the evening I’m zapped and try not to work unless it’s absolutely necessary.
Once I learned this about myself – and accepted that it was OK to not be able to peak at all hours of the day – I started strategizing my days. After a quick email check to ensure there’s nothing urgent, I tend to dive right into my most important work, typically a programming project. I have a morning routine, but it’s not lengthy: usually I’m working within an hour of waking up, a little longer if I’m commuting in to the warehouse. I’ll save unimportant emails, reading, writing blog posts, and other lighter work for later in the afternoon or early in the evening.
Programming in particular involves a juggling a lot of things in your head at once, so I think it’s especially vulnerable to decision fatigue. Being well-rested and in a clear mental state can result in much better work in much less time.