In my experience working on one thing for 8 hours isn't the most effective way to work. I find myself more effective when working on multiple tasks in one day i

In my experience working on one thing for 8 hours isn't the most effective way to work. I find myself more effective when working on multiple tasks in one day if they require thinking effort. A lot of the thinking doesn't get done when sitting in front of your keyboard, but rather when you are taking a shower or taking a walk. But passively thinking about a single thing during those activities doesn't exploit your thinking potential fully. You can't think that far ahead. If you have two projects you're working on, you can think a bit on one, and when you're stuck you think a bit on the other. When it actually comes to working, you have enough new material to work for a couple of hours on each project. This working will uncover new things to think about. If you instead work for 8 hours straight on a single thing, then after a couple of hours you'll hit things that require thinking before you can proceed, and doing that in front of your computer doesn't work but taking a walk or taking a shower isn't billable -- and even if it were I'd still get more work done when working on more than one project.