Uppercase "I"

One day, I was doing my French homework, and I started thinking about the way I write the letter "I". I write it vertically, without two horizontal lines on each end. Like this: I. And I realized... I didn't used to write it that way! I used to write it with the horizontal lines. I became consumed with curiosity of when this change happened. So, I consulted my faithful journal which I kept from late 2000 to early 2009 and I found out something very interesting...
On January 1, 2006, I was writing my "I's" with the horizontal lines. The next entry, which was January 26, 2006, the horizontal lines were gone!
Strange, non?
I'm wondering now, what in the world happened that made me start writing my "I's" differently? I'm fairly certain it wasn't an intentional change... Was there someone I knew who wrote their "I's" that way and I unknowingly picked it up from them?
It does make me wonder... and I don't think I shall ever know. *sigh*

On a similar note, I forgot how therapeutic writing in my journal is. Today I picked up my journal with the intention of only writing a few lines. I ended up writing a two page entry! It was wonderful. :)