Avoid scheduling your day so rigid that there's no wiggle room for the unexpected to happen. For example: You might live 10 minutes from your doctor's office but given all the other cars on the road, it will probably take you longer. Once at the doctor's office, you may expect to be called at your agreed upon appointment time but we all know the appointment time only applies to the patient side of the agreement. If your schedule is too rigid, you will spend time either rescheduling or running late to every other appointment.
So keep some wiggle room in your schedule so unexpected delays won't derail your day.