I drive a course in my Jeep and measure the odometer - checking waypoints along the way - i.e. the brick sign is 1/2 mile into the run, etc. I do this at several places, setting up different courses for myself - 3 mile, 4 mile, and 7 mile. I make sure that hills are included to vary the run and make it more difficult.
Also, it helps me to run with a buddy. If there is one thing I hate to do, it is to leave a nice warm bed to go run at 0 dark 30 in the freezing cold. If you have a running buddy there are at least two certified morons instead of just one - also you find that you push each other farther and faster than if you were just on your own - it is much easier to give up if no one is there to see you. If you don't have anyone inclined to run, check with your recruiter/OSO to see if there is another candidate in your area to run with.