Puppies play hard.

At a dog park where we are going, there are two areas for little dogs and big dogs. Luna is supposed to stay in the smaller dog's area, but she is willing to go to the big dog's; so I bring her there.
Luna thinks and behaves as she is a big dog...

Most big dogs are nice to Luna, but I have to keep an eye on Luna all the time. Some dogs play a little too hard to Luna.
As I talk with its owner, almost all such hyper dogs are puppies. They have too much energy and really want to play with Luna, but they have no idea about how to treat a little dog nicely.
Believe or not, most adult dogs know that they should treat a little one kindly. I am so impressed.