This is beautiful, there is newer version of this Poem available on internet as such ...

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.