I feel contrasts and conflict/hardships during your life really attribute to a great story. That sounds pretty mean/shallow but what I mean is that, if you have had some difficult times in your life during your MBA pursuit, mention them, mention how they affected you and then mention how you became stronger because of it.
A story like this will show progression in the sense that you came across a hard time and were able to get through it. Definitely mention how much it affected you, what you learned, and how you think differently as a result.
Overall, if you are simply talking about your work experience, again, pick a couple of instances where you learned something great, reflect on it and how it affected you, and how it made you a better person or better equipped to handle a similar situation in case it arises again.
Good for practice - type the story up and revisit it every couple of weeks/months. Build on it / reword some stuff you wrote earlier. This way, if you are interviewed and this question comes up, you will be better equipped at giving a great answer. You are basically trying to sum up your experiences and how you reacted proactively to them.
fwiw,
- tsd