A poor farmer asks a rich man for a donation of some food and hands him a plastic bag to fill up. The rich man says "I will give you a whole TRUCKFUL of food! You don't need this bag."
The poor man has never seen a truck, doesn't know what a truck is and asks that the rich man just fill up the bag.
We are the poor man. Hashem has limitless shefa [bounty] to shower upon us but our keilim are so deficient. He wants to bestow upon us such bracha but we are all too often satisfied with some crumbs.
[Sefer Yichud Hahisbodedus]