I also believe a big impetus to thankfulness--paradoxically according to the world's wisdom--is generosity with one's earthly resources. Our nature is to demand the physical blessings we believe we deserve. Hard to be grateful when you don't feel as if you have everything you're supposed to have.
We won't be thankful people until our hearts urge us to hasten our steps to Beulah Land. Our expectations then will be so fixed on eternity that we'll feel a little surprised--albeit pleasantly--when God blesses us with temporal comforts and luxuries. That's where thankfulness begins: with a heart that expects nothing, and so rejoices when it receives the unexpected.