it was only a little thing

John’s carelessness: John is a little boy who has a cart made of a box and four old wheels. He does not listen to his dad’s advice to fix a loose wheel with a nail, and thinks it is only a little thing.
The consequences: John’s cart causes a lot of trouble when he goes to buy carrots from the grocer. The loose wheel comes off and rolls into the road, where it scares a horse pulling a milkman’s cart. The horse runs away and the milkman’s cart falls into a canal. The milkman also falls into the water and gets wet.
The lesson: John realizes that his little thing has turned into a big thing, and he feels sorry for the milkman and the horse. He learns to be more careful and responsible in the future.