Well, no offense to the other posters and their equally valid views but I pose the other. Abeit from a differing perspective.
Grateful is defined as.....being warmly or deeply appreciative of kindness or benefits received: thankful.
As all benefit is not received but caused(to my view) I would hold not gratefulness for a kindness nor animosity for a unkindness. It being to my view caused, not by the giver nor the receiver as seperate from the gift. If I hold gratefulness for such things I would also have to hold animosity for the opposition of those things it seems. Why becomes the question then, why qualify the receipt of either. I do not thank myself for breathing or my heart for beating, these seem all caused, as all seems caused.
So I hold neither. If I find one person seperately able to give such things I would be grateful for them. I find none. They being caused to give such a thing and I being caused to receive such a thing, they cannot exist seperately from anything else, as neither can I. I may as well be grateful for myself as them, or for existance, or for causeitive factors themselves.
That in a perhaps ultimate consideration. Conventionally as I am grateful when I receive a meal I may pay for in a restaurant, and thank them when it arrives, I am grateful to all those mentioned.
Certainly I prostrate to Lamas when they are teaching and thank those that virtuously give me things. But it seems not to hold a large degree of significance.
So that is how I feel.
But that is just my personal view and not to be stated to be in any manner shape nor form superior to any other view. But it certainly differs from those offered.
"This order considers that progress can be achieved more rapidly during a single month of self-transformation through terrifying conditions in rough terrain and in "the abode of harmful forces" than through meditating for a period of three years in towns and monasteries"....Takpo Tashi Namgyal.