In my humble opinion, the cure for laziness at this point, is to let your
youngster grow up. He is truly a baby, both physically and
emotionally.
Big horses mature even later than smaller horses so he needs a few years to
"grow into himself". It may be just plain "hard" trying to move his
long legs and big size, with baby muscles.
In addition, his brain is geared towards eating and resting at this stage
of his life (growing), with a sprinkle of fun added, not work.
Once he is mature, you can work with his nature and help him understand
that going faster and more energetically can yield rewards. A treat can be
waiting at the other end of an arena, if he gives you the speed you want,
etc.
He may not be the impulsive horse you are wanting. Trying to "make
him" such, will probably make him sour. Or, he may be impulsive, and just
need time to "get there".
You can give him the time he needs to mature or you can risk any
host of issues by starting him too soon.
Karen Everhart MEd Co-founder and Executive
Director Rainbow Meadows Rescue and Retirement, Inc. Serving the equine
companions who have so loyally served us... www.rainbowmeadowsranch.com 620-725-3402
Owner/Operator Horse Calls - Equine Management
Solutions Centered Riding Instructor Distance Horse Conditioning and
Training www.horsecalls.com 316-648-5082