You must have the minimal story elements mentioned in ch. You can discuss the significance of your story explicitly, perhaps as a telling revelation sentence, or you can imply the significance via well chosen details. However, if you are a more advanced writer, be aware that statements of aboutness often close down meaning in ways that are insulting to a subtle reader. The subject areas you can find pivotal moments within are endless and totally based on what has happened in your life. Risky pivotal moments are often the hardest but most interesting stories to tell.
Risky stories can be very serious, but they can also be humorous.
Still, try to think about how much you are asking the reader to do. I would then freewrite about a few of those pivotal moments to see which one really makes me want to write. I would revise my freewrite based on some of those newly learned techniques. Finally I would edit its surface errors.