How can we thank Hashem for giving us everything we want?

Daniella Grodko asks: In Ashrei we say, "You open up Your Hand, and satisfy the desire of every living thing." I have learned that this sentence is to be said with much concentration. So much so, that if one does not have Kavanah while saying this sentence, he should repeat it. I don't understand why this line is so focused on. Yes, its a nice idea about G-d but why is it THAT amazing that it should be said again if the first time wasn't so great. I also don't think I can say this sentence truthfully according to the Artscroll's definition. How can I say that G-d satisfies all desires if I don't have everything that I want?

I have also wondered about this question, so thank you for spurring me to research it.
The Shulchan Aruch 51:7 is the source for the law that you state, that one should have extra concentration on the verse "You open Your hand..." Mishnah Berurah 51:15 explains why: "The whole reason Hazal instituted the practice to say Ashrei every day is for this pasuk, where we praise Hashem that He provides for His creatures." Rav Samson Rafael Hirsch (Germany, 1808-1888), in his peirush on Tehillim (Ashrei is Tehillim perek 145), agrees: this verse, he says, sums up the theme of perek 145 as a whole (and indeed of Pesukei de-Zimra itself): the universal order of God, which provides for every living thing. Rav Hirsch, however, also asks your question: "There are many who wait in vain for the fulfillment of their desires and indeed, there are people who are in want of the basic necessities of life!"

His answer is a bit complex.

Rav Hirsch explains that "You open Your Hand..." is a general statement, that all living creatures, including people, are sustained by God. Whatever we do get comes from Him, and He is capable of providing for all. But we - humans - don't necessarily get everything we want. It's true that the world in general is sustained by God without needing to justify or deserve it, but man in particular has special circumstances. We have intellect and free will and are subject to God's judgement as to whether we deserve to have our desires and needs fulfilled. Therefore, we say the next verse, "God is just in all His ways..." If we are not getting our desires fulfilled, it is a result of God's justice. "You open Your hand ..." is praise for Hashem's ability to benevolently run the world in general, but not for giving us each our own particular desires.