I tend to be the same way. I will be really motivated to exercise for a few days, maybe a week if I'm lucky, and then I get bored or it loses its flair. You've probably heard it before, but try getting a workout buddy; someone you can really have a mutual dependence with. That has helped me SO MUCH. I have been going to Curves for about three months, and this past month I really hit a slump but she has been going with me and making sure I go three days a week. You can do it! Here's a few of my faves:
-Don't focus on the now, but gaze ahead at what will be.
-What doesn't show in weight, probably shows in tape.
-If you keep doing what you've always done, you'll keep getting what you've always gotten.