When someone is gracious to you, the least you can do is acknowledge their graciousness. This does two things: It makes them feel good about their graciousness, and makes you feel special. Certainly, mutually beneficial.
People who are negative would ask why the graciousness? What is the ulterior motive? What a scarcity mentality.
The way you see the world is more a reflection of your image of the world, and not reality.
Be gracious, accept graciousness, and stay away from negativity!