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