Regardless of the reason for doing it, killing the dog in the story feels like a cheap emotional ploy. I think it's a common trap for new writers to fall into because we learn pretty quickly that "happy" stories are boring and even a little juvenile. Killing the dog is an easy way to impose grief on a reader because virtually everyone likes dogs.
When I first started college I found the whole experience somewhat perplexing. How do I keep up with all the coursework? How do I pretend to look interested in football? What even is a Student Union??? I attempted to track my progress throughout the year by listing my newfound knowledge in a Word document.