You probably don’t think of it this way, but everything you do “trains” the people around you how to treat you. Let employees interrupt your meetings or phone calls because of “emergencies,” and they’ll feel free to interrupt you anytime. Drop what you’re doing every time someone calls, and they’ll always expect immediate attention. Return emails immediately, and people will expect an immediate response.
In short, your actions give other people permission to keep you from working the way you work best.
A friend created an “emergency” email account; he responds to those immediately. Otherwise, his employees know he only checks his “standard” email a couple of times a day, and they act accordingly. Figure out how you work best and “train” the people around you to let you be as productive as you possibly can.