You can't Schedule Productivity

I tested, debugged and coded for most of the the day, by the afternoon, I was just too mentally tired to do anything else-- the afternoon was somewhat of a write off as I could not bring myself to learn a language for a light simulation program that I need to learn. I am coming to the conclusion that I have a limited attention span for certain activities, so why push it when you aren't going to be able to get any productive work done?

With that idea in mind, I have second thoughts about the 9-5 pm work day. Thing is that we aren't necessarily at our mental peak during this time period and hammering at a problem when not mentally prepared could be a waste of time. Just because a set time is designated to do something does not necessarily mean that it is the best time to do it. The human mind and emotions can be so fickle, unfortunately that it is just beyond the comprehension of logic-- it would be nice to be able to do something exactly when one decides to, but it doesn't work that way.

So I am here, stuck at the office, tired after programming and not in the mood to more work. It's 5 pm right now and it's just a matter of time before I can pack up shop and head home. The question I repeatedly ask myself, is time spent really the right metric to measure how much a company should pay a person?
Many of the brightest people I know do not follow the 9-5 syndrome. These people are writers, artists, engineers and hackers. Ideas come to them where ever they are and they work as long as they have to do whatever they have in mind. I've worked on projects well into the night because I thought it was something interesting to so, I've done the same for writing when an interesting idea hits. One of the things that I enjoy is having my iPhone where I am able to write immediately when a thought is fresh in my head instead of it becoming dulled after getting home.

Though it is important to have a form of daily rhythm/schedule, there are somethings that can't be scheduled for; and one of those things is setting a time when you are going to be mentally productive. Perhaps there are mental exercises to improve one's concentration and memory, but I have yet to find something that helps one to get into that "productivity zone." Some reading into human psychology might be something interesting to look into, but for now, I am going to give up on the notion that I am going to get a lot of productive coding work done and focus on other things instead.