I remember being in grade school and my grandparents were babysitting and took me to see my Great Grandmother. She lived alone in a small apartment, was from Poland, and at pretty senile at that point. My Grandma said she wouldn't recognize me.
She not only knew who I was but thanked me greatly as I was the only grandchild she had she always got a XMas card from all the time.
It was my Mom's idea to send the cards but looking back it just seemed nice I was able to do something for her that meant a lot.