Hi
aaaaatomic,
I completely understand what you mean. But as
Sia Admissions said, no one is expecting you to have changed the world or have saved thousands of people from starvation.
Talking specifically about the "achievement that you're most proud of"-essay, while you must be "real", you need to select an achievement that will help you advance in your admissions campaign. Unfortunately, having kept a promise most likely will not help you. But it all depends on how you frame it.
I always recommend to end the story with something like: "I am most proud of this achievement because ...”. If you are not able to finish the sentence, you must think about some other achievement. Ideally, you should end this sentence with an explanation of how the achievement had a huge impact on you as a person and/or as a professional. Also, remember that INSEAD is interested in what you learned from the experience and how it changed the way you keep relationships with others.
I hope this helps.
Feel free to reach out directly for a more detailed discussion about the essays or the application in general.
Good luck!
Alex