It wasn't until 2014 when I read The One Thing by Gary Keller that I really started thinking about how I could strategically organize my day. Keller proposes that a person should be a "maker in the morning and a manager in the afternoon." Ever since I read those words my mindset has been that the difficult "deep" work should be done in the morning while more managerial type work should be done in the afternoon. Other books (such as When by Daniel Pink and Tools of Titans by Tim Ferriss) also support the notion that, for most people, the work that needs the most concentration should be completed before lunch.
Keller also provides another outstanding takeaway, asking “What’s the one thing you can do, such that by doing it, everything else will be easier or unnecessary?" Many times upon entering the office for the morning I ask myself this same question and attempt to tackle the most important tasks in my job. These tasks could include projects, writing, and other "creative" work. Furthermore, I try to leave other "busy-work" - such as returning emails and writing personal notes - for the afternoon.