Want to leave the office by 5 p.m.? Start there and set that as your deadline, then work backwards to plan your day. First, make sure you schedule tasks you can control and get done without interruptions. The point being: you want to rule the day rather than letting it rule you.
In Eric Barker's popular blog, he interviewed Cal Newport, professor of computer science at Georgetown University, about how we can better manage our day and get more things done.
Newton, author of five books, including the well-received Deep Work: Rules for Focused Success in a Distracted World, explained, "Fix your ideal schedule, then work backwards to make everything fit--ruthlessly culling obligations, turning people down, becoming hard to reach, and shedding marginally useful tasks along the way. My experience in trying to make that fixed schedule a reality forces any number of really smart and useful in-the-moment productivity decisions."