In my OMAT team, we pick one reasonable and reachable goal for each month and work on that small goal for a whole month. By the time the month is done, you've now broken an old habit and created a new one! I've been doing this since September 2013 and it's the one thing that helped me finally budge the scale!
Here the name of our team if you are interested:
My OMAT Challenge (One Month At A Time)