[sxp62000]

I spend the first 70% of the work day on hard problems and things I absolutely have to get done. For me this 70% ends at 4pm.

At 4, I step out for a coffee, stroll around the block and grab a cookie. Then I come back to my table and reply to annoying emails and tackle the easy stuff till about 6-6:30.

I never start working on a tough problem after lunch, because if things go wrong, I end up working long hours and can't get it out of my head even when I go back home.

By the way, I'm really impressed that many people commenting here can work 6-10 hours at a stretch. I need to stretch every 45 minutes to 1 hour lol.