Miss Understanding

This is the third in a series of writing exercises that I came upon and assigned to myself. This latest has had me a bit stymied. "Write about something you wrote or did that you no longer understand." What? I used to understand, and now I don't? That concept is foreign to me. Maybe that is because I consider myself to be understanding to a fault. At one point in my life, I was known in a certain circle as "Miss Understanding." (Admittedly, this was a small circle, but I have owned the appellation ever since. I covet a reputation - more on that another time.)
.....Okay, I have let several days pass, while I thought about something - anything - that I have written or done that I no longer understand. At first, I thought of something I wrote in my journal during college - "Desire cannot replace fortitude." But frankly, I am not sure I even understood that when I wrote it! Or more accurately, my level of understanding has not changed since then.
.....Now I have let even more time pass. Still, I cannot conjure up a thing that I have done or written that I no longer understand. Unless it is the case that the level of my lack of understanding is so low that I don't even KNOW that I no longer understand, then I guess I am good to go on this one. I need to move past this once and for all!