There are generally two feelings towards time when you are working.
1. Time is going too fast!
2. Good gracious time is passing slowly today...
Let those emotions work for you!
When you sit down to work on your writing, establish a work schedule and make sure you record your time spent working. I recommend a spreadsheet “timesheet” because you can tally the number automatically, but it works just as well to record your time working on a simple piece of paper. Seeing the amount of time you are productive is motivational and keeps you wanting to be more productive. Conversely, seeing that you are not productive can spur you on to get more time in on your writing. Either way, be accountable for your time—even if only to yourself.
On another note, let your family and friends know what your writing schedule is and then strictly enforce it. If you work a 9-5 job at a bank, none of them would call or ask you to babysit or move furniture or just hang-out during your working hours at a bank so why would you not want them to take your writing time just as seriously?