original quote

Watch your thoughts; they become words.
Watch your words; they become actions.
Watch your actions; they become habits.
Watch your habits; they become character.
Watch your character; it becomes your destiny.
-- Frank Outlaw

This is actually a paraphrase of a Buddhist teaching called the "Dhammapada" which is attributed to the Buddha.

It reads:

The thought manifests as the word;
The word manifests as the deed;
The deed develops into habit;
And habit hardens into character;
So watch the thought and its ways with care,
And let it spring from love
Born out of concern for all beings....
As the shadow follows the body,
As we think, so we become.