Most Important Tasks
Organizing your day around your Most Important Task (MIT) is not an original concept. The idea is simple and effective. Each day, define the task you need to get done to advance your goals and work on it first. No matter what else you do that day, your MIT are the things you want to be sure you'll do. Some people define only one MIT each day, others use two or at most three.
However, there is an additional benefit of working around MITs that often gets overlooked. Defining the Most Important Task makes explicit what's important for you and what's not. It helps you make the necessary trade-offs to get things done.
Also, it will give your mind a north for your thoughts to drift toward when they are allowed to drift freely. Many times we "connect the dots" and find solutions to problems we've thought hard about precisely when we are doing other things, or after a good night's sleep. YCombinator founder Paul Graham writes about this brilliantly in The Top Idea in Your Mind:
Everyone who's worked on difficult problems is probably familiar with the phenomenon of working hard to figure something out, failing, and then suddenly seeing the answer a bit later while doing something else. There's a kind of thinking you do without trying to. I'm increasingly convinced this type of thinking is not merely helpful in solving hard problems, but necessary. The tricky part is, you can only control it indirectly.
I think most people have one top idea in their mind at any given time. That's the idea their thoughts will drift toward when they're allowed to drift freely. And this idea will thus tend to get all the benefit of that type of thinking, while others are starved of it. Which means it's a disaster to let the wrong idea become the top one in your mind.