This says so much

I saw a man pursuing the horizon;
Round and round they sped.
I was disturbed at this;
I accosted the man.

"It is futile." I said.
"You can never-"

"You lie" he cried,
And ran on.

-Stephen Crane (1895)

I love this poem. It's for every 'realistic' person who told a 'dreamer' that something wasn't possible.