I was typically ungrateful in my teens and twenties, waiting for the next handout, complaining loudly when it was slow in coming, and complaining about a lot of other things too.
Things changed a bit when I had kids. They changed a lot when I helped care for my dying father. It was in the act of caring for him in a way that he could not care for himself that I came to genuinely love him beyond what I thought he had to offer me. It set the stage for missing him the way I do now, eleven years later.
It also helped me understand that thankfulness is a byproduct of generosity. Someone who is not looking for ways to give and sacrifice for others will never be thankful.
Like other parents and teachers, I daily pour my heart and soul into the lives of others who rarely express thankfulness. As I grow older and am spread increasingly thinner across impossible obligations and responsibilities, there are days when I can barely press on. What drives me onward is not the will to have but the will to give. My capacity for love is the result of what I invest in others, not what they invest in me.
For me, the newest aspect of this epiphany is the realization that in allowing others to care for me in my most helpless, vulnerable moments I am actually allowing them to really love me, perhaps for the first time.