Beautiful girl :) What are you feeding her?
Some horses don't handle stuff like oats and sweet feed well, and henceforth get hot and harder to handle.
You want to either look into getting a grain were the horse gets energy from vegetable fats (Purina Strategy is what I use). Or, taking her off grain completely and giving only supplements.
Weight wise, she could be fitter, but otherwise looks just fine.
As for wanting to go-go-go, I would suggest, if possible, doing simple patterns at a walk with her. My own gelding is quite high strung and spooky, and merely walking patterns around trees relaxes him, and makes him more responsive and easier to ride.
It takes a little while, but generally after about 10-15 minuets I find that the horse stops trying to rush and goes along quietly and easily. It varies from horse to horse, some calm down quicker than others.
After I feel that he is calm and connected (listening to what I'm saying to him) I do brief stints of trotting in between the trees (or barrels, poles, cones) at random times. If he starts trying to rush and get his head all up in the clouds, it's back to doing those simple patterns again :)
Patterns have worked wonders for my nine-year. He once down-right exploded at the sight of a marriage mobile and was rather difficult to stop. After he was stopped, turned around, and back out were he was before I continued circling trees. He went from wide-eyed-tremble-hyper-rushing-gotta-go-gotta-go to relaxed, calm, and enjoyable.
Good luck with your girl, she has absolutely beautiful eyes.
Wait! I'll fix it....