"Is it more important to get what you want? Or to make the most of what you've got?"
My father used to pose this question to me when I was little and he found me over-emphasizing the former, to the disregard of the latter. Back then, I understood that the latter was the desired answer. I saw things in relatively starker black-and-white in my youth.
As I matured, I continued to ponder the question. At first, I came to the dissident conclusion that both were equally important, in conjunction with moderation. I saw the danger of stagnation by maximizing contentment and minimizing drive, and, on the other side, the danger of dissatisfaction by maximizing ambition and minimizing appreciation.
Later, I decided that it was much better to make the most of what you have, for as far as the Universe is concerned, It has already given you everything. Additionally, I saw that you can never get what you want if you cannot want what you get. (On a slight aside: I really like the Gnarls Barkley line, "Anyone who needs what they want and doesn't want what they need, I want nothing to do with.")
Now, while pondering the potency of gratitude, I am thinking that it is better considered as a matter of sequence: Both are equally important, but you must first value that which you possess, before you can acquire that for which you yearn. In fact, starting from gratitude will deliver you to achievement.
Gratitude is a truly magnificent force. Without it, all you accomplish is worthless, for the only worth relevant to your life is that which you assign. With it, however, you can find joy in every atom of Creation. Since thoughts become things, it is better to focus on abundance rather than lack, for our mindset perpetuates our state of being. Failing to appreciate what you have leaves your sights aimed at what is lacking, and you then live in a world of need, want, longing, and desire - suffering, if you want to invoke Buddha. When you spend your energy giving thanks for your belongings (intangible as well as tangible), you enjoy a world of fulfillment. They say that like attracts like, so... why would you do otherwise? That's my question: Why not employ as much gratitude as every cell of you can muster?