It can certainly be difficult to maintain a positive attitude throughout your entire study plan. As with all things, some days will be good, and others bad. That's life.
You might feel particularly overwhelmed once you think of the big picture. Nobody can handle thinking about the GMAT, MBA, and life and family afterward. It's simply too much. Just focus on what you have to do today
and things will fall into place. Just take things one step at a time. It's much easier to accomplish smaller goals. Eventually, things will add up.
YourDreamTheater has a good point; read some of the GMAT Experience topics. That helped me, especially when I needed a break.
GMAT Club Premium Membership - big benefits and savings