I don’t remember the exact age, maybe ten or in my early teens, when my dad gave me a copy of a poem on cardboard backing. Many times the poem has come to mind and some years ago i found it online. It’s often listed as “anonymous” but then i saw: “The original Poem was entitled "The Guy in the Glass" and was written by Dale Wimbrow in 1934. The original poem is slightly different.” And of course the title could include “woman” or whatever one calls one’s self.
The poem came to mind again recently, as am working on a short story told from the perspective of the mirror. The poem gives good advice and a good reminder, especially nowadays when many people get obsessed with social media “likes” and physical appearances; so i share it here:
The Man in the Glass
When you get what you want in your struggle for self
and the world makes you king for a day
Just go to the mirror and look at yourself
and see what that man has to say
For it isn't your father or mother or wife
who judgment upon you must pass
The fellow whose verdict counts the most in your life
is the one staring back from the glass
Some people may think you a straight-shooting chum
and call you a wonderful guy
But the guy in the glass says you're only a bum
if you can't look him straight in the eye
He's the fellow to please never mind all the rest
for he's with you clear up to the end
And you've passed your most dangerous difficult test
if the man in the glass is your friend
You may fool the whole world down the pathway
of life and get pats on the back as pass
But your final reward will be heartaches and
tears if you've cheated the man in the glass.
PS
To that i’ll add one of my dad’s pithy sayings:
”You’d better like yourself.
You’re with yourself 24 hours a day.”
PPS
In my teens (with braces, and hair i now envy) with my dad, in one of those photo booths.

Peter, your comment brings to mind that there is an ongoing inner journey or wrestling match each person can have with regard to self-likes and dislikes, yet as long as self-hatred is left out of the equation, personal change for the better is readily available.
"You’d better like yourself.
You’re with yourself 24 hours a day.”
Indeed... if you hate yourself you'll be of no use to others no matter how much you 'help'