I get nostalgic and often sad when I look at childhood photos just because of knowing how much time has gone by, how when I was a child I never thought about life going on and getting older.

It could be that something happened when you were in 1st grade that you can't remember but it made you sad. It doesn't have to be traumatic. Do you have other photos from that same age? Is it only this one particular photo that makes you sad? Maybe you should bring it with you to your next session and see what happens.

There's a photo of me that I call my "shy" picture. My eyes look shy or questioning, I'm not sure. I have shown it and other childhood photos to my T. Nothing has come up from showing her but maybe it will for you.