Most tasks at your job fall into one of two categories: mental and mechanical. Mental tasks require focus and cognitive thought, while mechanical tasks can be done whether your mind wanders or not. Save the latter for later, when you're not at your peak.
Picture: Butler University/Flickr
As productivity blog MakeUseOf points out, you don't need your brain to be at peak focus for tasks like stuffing envelopes or moving boxes from one place to another. So, when you're at your peak in the morning (or whenever the peak is for you), don't waste your focus on the menial tasks. Dedicate that time to getting the more taxing mental tasks done:
In everyone's work life, there are some projects that require your full mental faculties, while other tasks are more mechanical in nature. Successfully prioritising these items means can help you dig yourself out of task backlogs. For example, writing an article is where I need to be alert, but the process of uploading and formatting is mechanical and all about going through the motions. By prioritizing, I can tackle my articles when my concentration levels are high, and save the tedious work for later.
Of course, if that's not how your brain operates, you can adjust. For example, night owls may not be at their most productive first thing in the morning, which would make that a great time for simpler tasks. Saving the more in-depth stuff for later would be beneficial to them. The point is to do the right task at the right time according to your own mental habits.