No phone calls, no emails, no websites, no chit chatting, no meetings, no talking to people, no goofing off, no reading the
newspaper, no relaxing with a book, no snack breaks, no errands, no paying bills, no putting out fires.
For the first four hours of each day, work on your project, whatever that may be.
If you are a programmer, write software for four hours.
If you are a PhD candidate, spend those four hours on your dissertation.
If you are a writer, write for four hours.