Self image is highly subjective and what you see in the mirror is influenced by what you ate or drank, how the lighting is positioned, your mood at that moment etc etc...

I didn't say it's perfectly accurate, but enough to see when things are getting bad enough.

Didn’t work for me until I saw pictures of myself where I didn’t recognise myself.

I saw a picture from behind and didn’t think I saw that person at my friends wedding, but then realised it was actually me, and I was not the shape I thought I was.

i hope in a positive way :)

No, I was much fatter than I appeared to myself in the mirror.

It lead to a health journey, but the gradual fattening wasn't visible until I saw myself with "fresh eyes".