How much work do you actually get done in a day? Most people sit down to work for 8 or so hours a day but actually spend less than 30% of that time checking things off their list.
If you actually want to get things done you need to guard your attention, avoid distractions, and stay focused AF.
The best way to make this happen is pretty simple. Put in noise-canceling headphones, turn off ALL digital notifications (mobile and desktop), avoid distractions using the Pomodoro Technique, ask not to be bothered by coworkers unless it is an emergency, stay focused on one task at a time, and you will get more done in 6 hours than most can in 10.
It really is that simple. Execution can be a lot of work, but the process is pretty straight forward.
Keep the axe sharp.