As a young child of an age of 3 or 4, I remember playing in the sand box with my fellow comrades. We were having a jolly time digging holes and little sand structures in the sand box with our tiny construction tools. As I was minding my own business, I hear my friend start crying and I turn my head to see an older kid, probably around 5 taking her shovel. Since I was a pretty big child, I go the kid and push him down for taking the shovel. I grab the shovel from his hand and give it back to my friend. After pushing the kid down, I remember me and the bully being scolded by our parents for causing a problem in the sand box.
It's honestly not that interesting that you remembered this memory. It was most likely the first time you were exercising control over something, as before that it was probably parents, or older kids like that bully. It makes sense you would remember your first brush with being the authority on something! Tis a big landmark!
Going on what the previous reply said, my memory is somewhat similar. I had an unfriendly encounter with someone who ticked me off and for that reason, it became a memory which lasted for 20 years. Not sure if my memory is accurate, but either way it's quite interesting.