Each morning, we get a brief window of time during which we're most mentally capable of getting stuff done, said behavioral scientist Dan Ariely in a recent Ask Me Anything on Reddit. And yet most of us waste that time. 

Generally speaking, Ariely said, the two hours after we become fully awake are, potentially, our most productive. But what's the first thing you do when your brain shakes off the fogginess of sleep? I know what I do: I ease into the day by attending to my most mindless tasks first, like replying to emails or playing around on Twitter. Ariely really wishes we would knock this off. 

One of the saddest mistakes in time management is the propensity of people to spend the two most productive hours of their day on things that don't require high cognitive capacity (like social media). If we could salvage those precious hours, most of us would be much more successful in accomplishing what we truly want. 

One way to fight against this tendency is to decide the night before what you want to accomplish in the morning, so you can jump right into your day. There is a time for mindlessness, but maybe save it for later. 

This piece was originally published on "Science of Us," New York magazine's science blog.