Time block your calendar
Assign every important task a specific slot on your calendar. Unscheduled work tends to expand or never happen; scheduled work gets done.
Leave buffer time between blocks so one overrun doesn't collapse your whole day.
Use the Eisenhower matrix
Sort tasks by urgent vs. important. Do the important-and-urgent now, schedule the important-but-not-urgent, delegate the urgent-but-unimportant, and delete the rest.
This single filter prevents you from spending your best hours on other people's priorities.