The power of habit

Assume a virtue if you have it not.
That monster custom, who all sense doth eat
Of habits evil, is angel yet in this:
That to the use of actions fair and good
He likewise gives a frock or livery
That aptly is put on. Refrain tonight,
And that shall lend a kind of easiness
To the next abstinence, the next more easy;
For use almost can change the stamp of nature,
And either shame the devil or throw him out
With wondrous potency.

William Shakespeare - Hamlet
(The New Oxford Shakespeare - The Complete Works, Modern Critical Edition)

(Habit is a terrible thing, in that it’s easy to get used to doing evil without feeling bad about it. But it’s also a good thing, in that being good can also become a habit.
Say no to sex tonight, and that will make it easier to say no the next time, and still easier the time after that. Habit can change even one’s natural instincts, and either rein in the devil in us, or kick him out.[No Fear Shakespeare])

Man's only power - his MIND

Man cannot survive except through his mind. He comes on earth unarmed. His brain is his only weapon. Animals obtain food by force. Man has no claws, no fangs, no horns, no great strength of muscle. He must plant his food or hunt it. To plant, he needs a process of thought. To hunt, he needs weapons, and to make weapons - a process of though. From this simple necessity to the highest religious abstraction, from the wheel to the skyscraper, everything we are and everything we have comes from a single attribute of man - the function of his reasoning mind.

Ayn Rand - The Fountainhead