Carry a schedule and record all of your thoughts, conversations, and activities for a week. This will help you understand how much you can get done during the course of a day and where your precious moments are going.
Take five minutes before every call and task to decide what result you want to attain. This will help you know what success looks like before you start, and it will slow time down.
Put up a "Do Not Disturb" sign when you absolutely have to get work done.