This HBR article hits the spot - how to stop doing stuff that is of low value in your day to day job - and focus on what matters.
In the past, time management experts would recommend that you divide up your work into A tasks, B tasks, and C tasks. The concept was to do the A tasks first, then the B tasks, then the C tasks, when you can get to them. If priorities changed, you just changed the order of your As, Bs, and Cs. Doing all aspects of a job seemed possible then, if you just followed some basic time management rules.