The sign for "horse" is made by forming the letter "u" (or "h") with your right hand. Place your thumb on your right temple, or a little higher. Bend and unbend your first two fingers a couple times.
If you use all the fingers instead of just the index and middle finger this sign means "donkey." If you sign "donkey" but only move the fingers from the upright position to the bent position (one single, quick motion) and don't move them back--then you have signed "stubborn." --Think of how some animals bend their ears down when they are behaving stubbornly.