My Halo

I saw a peom by Margaret Ingall:

I POLISHED up my halo
As brightly as I could,
I wanted folks to see it
And know that I was good.
Yet quickly did I notice,
And very odd it seemed -
The harder that I polished,
The duller that it gleamed.
So giving up my effort,
For pointless seemed my zest,
I put away my halo
And simply did my best.
But stranger still to tell you
Since putting it away,
I've noticed that my halo
Shines brighter every day!