I probably shouldn't talk since I'm posting on HN instead of doing my work right now...
But I find it helps to break things down into tasks that'll take no more than 2-3 hours, and then pick 2-3 tasks I'll do for the day. Once I'm done with those, I'm officially done for the day, though if there're some obvious things I could do quickly, I'll usually want to just do them since I've been so productive. ;-)
You need downtime in order to stay productive. I've found that if I just work constantly and let the days bleed together, I lose my focus and end up getting a lot less done than if I decide what I want to do, do it, and then do whatever I want.
But I find it helps to break things down into tasks that'll take no more than 2-3 hours, and then pick 2-3 tasks I'll do for the day. Once I'm done with those, I'm officially done for the day, though if there're some obvious things I could do quickly, I'll usually want to just do them since I've been so productive. ;-)
You need downtime in order to stay productive. I've found that if I just work constantly and let the days bleed together, I lose my focus and end up getting a lot less done than if I decide what I want to do, do it, and then do whatever I want.