My initial reaction to this was, "I don't know what this is about but there must be some profound hidden meaning to it!"
A few month later, I was notified that my graduate school application which I spent the past decade constructing was not fruitful. Disappointed, and wretched. The news came to me as if that email was sneering at me, poking the scars formed to protect my fragile insecurities, fears, and pride. I didn't know what to do for a while but to be overwhelmed with the flood of emotions. After a few hours of crying, which felt like letting go of my desire for control, I was left with emptiness.
Then miraculously, hope came. The struggles I had in the past have increased my tolerance for failure. As long as I do not give up my goals, I can always work towards it. It was then that I remembered the reference to stones in the jar. The larger stones are failures, misfortunate, sickness, and the spaces in the jar can be hope, persistence, and conquer.
The person who said this to me had once lost everything: career, friends, family, even his homeland. A person like that has every reason to be bitter about this world, however, he displayed an inner happiness and peace that I rarely see in others.