It Takes Mental Energy To Create

Humans seem to constantly forget about fuel sources. Cars will run out of gas. Candles burn themselves out. Guns need bullets. Somehow (by which I mean because of watching too many movies), we often think of energy as free, but everything has a cost, including thinking and creativity. 

It takes mental energy to create. You are burning calories and using vitamins and minerals to fire your neurons and make new connections. If you don't have enough energy, then you simply putter around. 

The advice is often given to write in the late night or early morning, and there is some value to that, but those also are times where mental energy is not optimal.

There is a balance you need to find to do it properly. On one end, you have no energy, and on the other you have no creativity. 

Experiment to find that balance. They can be your best hours for writing.