excerise is certainly difficult to stick with unless you try and stay motivated. i know that its tough but when you keep your goal in mind it becomes easier. also, when you start achieving results you see that you really are strong enough to change your life and that motivates you more. you can do, just keep thinking about the finish line :)
what i do is associate exercise with something, i get a BIG glass of ice water and workout, soon whenever i drink ice water i get the urge to exercise. like pavlov's dog.