It also serves as a template against which one can hold oneself in later years.

My high-school yearbooks portray me as a performer, a musician, and an artist. I'm none of those things now. Well, maybe musician a little, and it's been said that coding is an art...

Yearbook signatures carry a tenor of captured time--a musty sense of personal history. My Senior year, the girl I was dating (then, a Junior) wrote:

Hello Daniel,
God I'm going to miss you, we've been such good friends and I never want to give this up. At least you're stuck in the state for the summer like the rest of us losers, and myself. Will you miss us? Will you miss me? I hope everything works out for you, you are one of the most wonderful, beautiful people I have ever known. I hope everything works out for us. There should be a lot of fun ahead.
Love,
Rebecca

The fact that she broke up with me less than a month later doesn't change the sentiment that I feel on re-reading that.