I don't know. I was very, very depressed one day when I went into a convenience store; and the clerk said hello and gave me such a bright smile, it broke my dark mood. I thanked God for her. She may not have known what a great kindness she did me. I know nothing else about her; but to me, she was a saint, and I asked God to reward her.
As I thought about it, this came to mind:
Matthew 10:42 And whosoever shall give to drink unto one of these little ones a cup of cold water only in the name of a disciple, verily I say unto you, he shall in no wise lose his reward.
It looked so unimportant in one way; but her "small deed" of kindness was what I needed. You might even say the "seed" of life planted in me needed watering and she gave me water.
How does she look at herself? I doubt she thinks she's great; and I think that meant God could use her in a way that even she didn't understand. She may have thought of herself as a lowly clerk in a store; but I could feel the Holy Spirit moving. I think it's harder for the people with grand ideas about themselves.