Context switching is expensive. Every time you switch from one type of task to another, your brain needs time to adjust. Group similar tasks together and do them all at once. This is called batch processing.
Do all your phone calls at once. Process all your emails in one session. Run all your errands in one trip. Handle all your administrative tasks together. This reduces switching costs and makes repetitive work more efficient.
Batch processing also helps you get into a rhythm. Once you are in the flow of making calls or processing emails, you can move through them quickly. The momentum carries you forward.
Look at your tasks for today. Group similar ones together. Do all of one type before moving to the next. Notice how much faster you work when you reduce context switching.