You might think a good manager should always be accessible when in the office. But, if every spare minute is filled with people walking through your door eager for attention, you'll never get anything done. Change your standards for what it means to be an effective boss. Part of being a good manager is demonstrating focus on high-priority work. It's OK to keep your door closed at times. Setting boundaries for yourself and your employees helps get your work done. You don't always need to explain why you're setting those limits, either. You can simply say, "I have to go," or "I'm sorry but I can't come help right now; please send me an email instead."
Source: Today's Management Tip was adapted from "Stop Being a People-Pleaser" by Elizabeth Grace Saunders.