I find that I cannot write code at top quality for more than about 6 hours a day. IMHO, most programmers aren't able to write at their top skill level for more

I find that I cannot write code at top quality for more than about 6 hours a day. IMHO, most programmers aren't able to write at their top skill level for more than that, but don't realize this about themselves. Factoring in time to handle my mails, some meetings, and that 6 hours adds up to a working day. If I program private projects after hours, I get grumpier and less focused. For my own health and sense of accomplishment, I need to stop coding at the end of the working day. I don't switch off entirely. I do read tech books during my evenings, but that's a non-creative activity, so my coding doesn't suffer from it.