[smilefreak]

This is exactly my experience, recently I have sometimes worked 9-5 got nothing done and gone home feeling like shit for being so unproductive. Then, to make up for it, I would find myself working some late nights and always made up for the lack of outputs. I now just start late and work late, which actually means I get more free time because I don't need to make up for anything.

As in interesting point, when I was working 9-5, I noticed that most people at work were incredibly unproductive all day so maybe it is somewhat a social construct also. When alone at night without distractions, without the context of people slacking off, I find it far easier to get focused and I don't just talk nonsense to anyone nearby.