Same as post above. When I bought Buck the owner said he likes to go, he's not a kids horse. When my 11 year old gets on him I taught her when he picks up speed you didn't ask for, ask for his head to come in and touch your foot ( when she started doing this at first, he would circle a bit) basically it's telling him "wrong" come to a complete stop and start over. After about 10 mins with this I was able to take my daughter on a long ride with another horse out into the country with no problems. Someone once told me "it's easy to get a horse to run, much harder to get them to just walk". But this worked for my daughter and I've used it to get Buck to hold his speed in his gates.
The hardest thing about learning to ride is the ground!