Pull the reins!

Hold your reins properly in a firm hand. Up!

He just feels when to let it go, and how much.

I'm sure sorry, ma'am. He jerked the leash right out of my hand.

Quicker than we can say it, the whole party were over the fence, making with all speed for the rocks, while Michael, throwing himself from his horse, and fastening the bridle to the wagon, began driving it rapidly away.