Grateful, Content and Appreciative

I am not sure what you call them, characteristics, qualities, values? Whatever they are, I want my beauties to have them, or to be them.  I am really struggling with how to infuse these qualities (or whatever they are) in my darlings. My blood starts to boil when we are doing something special and all I hear is complaints or whining. Makes me want to stop doing nice things for them...

Could it be because they don't view going out to eat as a special treat, because we do it so often? Am I ruining their ability to appreciate and be grateful because it is business-as-usual for them?

Do they not know how to be on their best behavior when we go out and do something special because we do those things far too often?

Picture Avery running across the bench seats at Wendy's Last Night & Picture Olivia crying about her Vanilla Frosty and about wanting another treat when she got home. How do you get your children to stand quietly next to you while your order, and to say "thank you Mommy, I know you didn't have to do this for us, and I appreciate you trying to do something nice and special for us and with us, you are the best".

Another good example is last Halloween - we had trick or treating at work, one little boy reached into a HUGE bowl of candy and took one piece, we all told him he could take another and he said "no, thank you this is enough" and when Olivia was faced with the same candy bowl it took every ounce of my strength to prevent her from dumping the entire bowl of candy into her treat bag - why? What have I done to always make them want more, to not be happy with what they have?

And these days everything is a competition between Olivia and Avery.  Olivia got invited to a Birthday Party for a friend at school - she went and Avery and I hung out.  Avery got invited to one of her friends Birthday Parties and it was the end of Olivia's life as she knew it. The girl fell apart.  She wasn't grateful that she had been to Carter's Party, she was beyond upset that she wasn't going to Ivy's Party and Avery was.  If Avery gets something, Olivia needs it, EVEN if she doesn't want it.  She can't just be happy with what she has.  I don't want that life for them. I want them to be content in ways that it matters, but strive to want more in other ways, if that makes any sense? How do you teach them when to want more? Like when you get a 75 on a test, don't be content, work hard and work towards that 90, but when Avery gets 4 chips and Olivia gets 3.99 chips, it isn't appropriate to throw yourself on the floor and fall apart.

I am at a loss, I am not doing a good job leading in this space. I often find that I am not as content as I would like to be.  I generally feel as though I am grateful and appreciative of what I have, and don't fuss to have more, but I would like to work on the contentment piece. Maybe we can all work on it together? But how?