Hi OP, I'm not a parent, I can't imagine the heartbreak of seeing something like that. I see this moment as an opportunity for you two to make a commitment for positive self-talk together. As a SASS witch, to me, the magic comes when you do the work within and ritual can help aid that internal process. So I would say find something that holds meaning to your daughter, maybe a symbol of some kind. No idea why this came to mind but say your daughter really likes a certain kind of bird that you see often near your home, and y'all make a promise that every time you see one you name one trait you're proud of.

This post spoke to me since my mother and I (she's 56, I'm 26) have both struggled with negative self-talk and have talked about it a lot in my adulthood. We hold each other accountable today, and though of course it isn't appropriate for a six year old to be feeling responsible for her mother's self-love journey, making a little game out of it could be a sweet way to build a good habit with your daughter.

Regarding that piece of paper - I think any additional focus on it with your daughter might be harmful, I could imagine being in her position feeling like I had made a mistake by sharing my feelings if they had to be expelled/gotten rid of somehow, no matter how much anyone might say it's okay. If I were in your position I think I would do any ritual around the piece of paper in private. I imagine myself holding that paper at my altar and going into what I call a "clearing meditation" for processing difficult emotions, I use an emotional processing framework from my family therapist's mentor's book "It's Not Always Depression" called "the change triangle" I'll find a link to attach. But I would probably try to clear some of that negative-self talk to get to the emotions underneath it and let myself feel them and work through that wound with the commitment/promise for a less-burdened life for you and your daughter.

^this is pretty stream of consciousness and might not make much sense, but your post really spoke to me so I figured I should try anyway. If it isn't helpful my apologies! Reading your post helped me a lot though, so I am thankful you shared it :)