When you want to catch a fish, I'm told that the best time to cast your line is either early in the morning or during the evening. It's then that you're most likely to bag a big'un. A week or so ago I was wondering what time of day I'm at my most productive, so I decided to carry out a little investigation. I reckoned that a rough and ready way to measure it would be to check the creation dates and times of all the files on my computer's hard drive.
Now I know this wouldn't work for everyone, but my work tends to generate lots of smallish files. If I were a more regular kind of author I'd probably spend my time adding to one enormous document; however, my own working style generally involves producing one thing, saving it, then moving on to another - and so on. What did I learn then? Monday and Friday, it seems, are my least productive days. However, from Tuesday to Thursday, when I appear to be firing on all cylinders, I tend to do a lot of my work in the hours immediately following 1pm and 7pm. Strange, I know, because this is probably when most normal people sit down to eat. (Don't tell my mum.)
Having even a sketchy concept of the times at which you're likely to be your best makes sound sense. Perhaps you won't find a way to get to your numbers as easily as I did, but simply reflecting on it should at least give you a rough idea of when it makes sense for you to do the stuff you need to do every day, then perhaps you can tweak your schedule accordingly. No sense fishing when they're not biting.