My first memory is from when I was three. I had just entered preschool, and I became friends with a boy named Michael. I was really smitten with him. I remember asking him to play in the sand with me. I don't think there was anything about it that made it particularly memorable.
I also remember a few other things from preschool, such as pinching my teacher for no good reason, playing with the paper that changes colors in the sun, pretending to read, and playing with a hose in the summer time. I vividly remember falling down and scraping my knee, but not telling any of the teachers because I didn't want them to fuss over me.
Although I know I've changed, I still feel the same. I don't feel like a different person at all. I remember thinking, when I was really young, that I didn't feel young at all, I just felt like me. Now, I don't feel older, I just still feel like me.
This reminds me a lot of the way that my earliest memories are. When I look back on preschool, I definitely remember bits and pieces, much as you have described- things like everyone wanting to play with the lite-brite in the corner, and the dinosaur cake my best friends had on their birthday (they were twins), and building houses out of big blocks. Also, the same way you say you know you've changed but don't feel like a different person, I definitely feel the same way. At my elementary school, we had something called "meeting for worship" where we would sit in silence, and if you felt like you had something to say that was important, you could stand up and say it. (I went to a Quaker school). The only time I ever stood up was when I was in 4th grade, and I said something like "I'm in fourth grade now, but I still feel the same as when I was in kindergarten". Which, basically what I was trying to say was that when I thought back I still felt like the same person. It's a very hard feeling to put into words, but it's like, I can always put myself back in that first person mindset with the feelings and thoughts at the time of the memory, and so I don't feel like I've changed too much. Your quote about not feeling young when you were young, just feeling like yourself definitely sums up how I've always felt.
I agree that a lot of my earliest memories are more like moments or quick images than more drawn out stories. Most of them are just the piecing together of these shorter memories. I also thought that your description of how you feel now as related to your younger self describes how I feel, that even with changes overall you are the same. As much as I can recognize the differences it is still hard to see how they could have made me feel like a different person.