This has always been one of my favorites.

The Man In The Glass

When you get what you want in your struggle with life
And the world makes you a king for a day,
Then go to the mirror and look at yourself
And see what that guy has to say.

For it isn't your father, or mother, or wife
Whose judgement upon you must pass;
The fellow whose verdict counts most in your life
Is the man staring back from the glass

He's the man to please, never mind all the rest;
For he stays with you to the end;
And you've passed your most dangerous, difficult test
If the man in the glass is your friend.

You may mimic Jack Horner and chisel a plum
And think you are a wonderful guy;
But the man in the glass says you're only a bum
If you can't look him straight in the eye.

You can fool the whole world down the pathway of years
and get pats on the back as you pass;
But your final reward will be heartache and tears
If you've cheated the man in the glass.