These pictures are of Lena, a littermate to Sally and Tessa, and my mom. Lena has developed an unusual passion for spreading hay. These passions are a useful training opportunity for a potential stockdog puppy. After all, a lot of herding involves self control of a dog's first impulse, as in "I'd really like to rush in and bite those sheep, but have learned that it works a lot better to go slow and give them a chance to move off".
So once you have found a passion in your future stockdog puppy you then have two options: get them to give it up, as I do with my puppies when they attack my broom or my rake, or my wheelbarrow tire etc, etc. Or you put it under your control, as my mom is doing with Lena's hay spreading. So you teach the dog to wait for a signal before starting the fun activity and you teach them to quit on command. This learning carries over well to the start/stop aspect of herding. Ok, go get'em vs. that'll do.
If you just let the pup go ahead with whatever it's doing because it's cute and funny you will have a devil of a time getting contol later.