As A Man Thinketh by James Allen

Mind is the Master power that moulds and makes,
And Man is Mind, and evermore he takes
The tool of Thought, and, shaping what he wills,
Brings forth a thousand joys, a thousand ills:—
He thinks in secret, and it comes to pass:
Environment is but his looking-glass.
“As a man thinketh in his heart, so is he.” The sum of a man’s thoughts are his character. His character influences the conditions and circumstances of his life. Every action springs forth first from thought – even actions considered to be spontaneous and unpremeditated.
Act is the blossom of thought, and joy and suffering are its fruit.
The law of cause and effect exists in the world of thought, not just the natural world. A God-like character is the result of God-like thoughts. A bestial character is the result of groveling thoughts. Man is made or unmade by his own thoughts, which can destroy him or build him up. Man becomes master of his “household” of thoughts, by application, self-analysis and experience.