Remember, it is not enough to be hit or insulted to be harmed, you must believe
that you are being harmed. If someone succeeds in provoking you, realize that
your mind is complicit in the provocation. Which is why it is essential that we
not respond impulsively to impressions; take a moment before reacting, and you
will find it easier to maintain control.
— Epictetus, The Art of Living: The Classical Manual on Virtue, Happiness and Effectiveness
Man can do what he wills but he cannot will what he wills.
— Arthur Schopenhauer, Essays and Aphorisms
Plans are worthless, but planning is everything.
— Dwight D. Eisenhower
There is nothing either good or bad, but thinking makes it so.
— William Shakespear, Hamlet