Ah, beware of snobbery; it is the unwelcome recognition of one's own past failings.
Cary Grant

Better beware of notions like genius and inspiration; they are a sort of magic wand and should be used sparingly by anybody who wants to see things clearly.
Jose Ortega y Gasset

Beware how you take away hope from another human being.
Oliver Wendell Holmes

Beware how you take away hope from any human being.
Oliver Wendell Holmes, Jr.

Beware how you trifle with your marvelous inheritance, this great land of ordered liberty, for if we stumble and fall, freedom and civilization everywhere will go down in ruin.
Henry Cabot Lodge

Beware lest in your anxiety to avoid war you obtain a master.
Demosthenes

Beware lest you lose the substance by grasping at the shadow.
Aesop

Beware of a man with manners.
Eudora Welty

Beware of all enterprises that require a new set of clothes.
Henry David Thoreau

Beware of bugs in the above code; I have only proved it correct, not tried it.
Donald Knuth

Beware of endeavoring to become a great man in a hurry. One such attempt in ten thousand may succeed. These are fearful odds.
Benjamin Disraeli

Beware of false knowledge; it is more dangerous than ignorance.
George Bernard Shaw

Beware of geeks bearing formulas.
Warren Buffett

Beware of him that is slow to anger; for when it is long coming, it is the stronger when it comes, and the longer kept. Abused patience turns to fury.
Francis Quarles

Beware of him who hates the laugh of a child.
Henry Ward Beecher

Beware of little expenses. A small leak will sink a great ship.
Benjamin Franklin

Beware of men who cry. It's true that men who cry are sensitive to and in touch with feelings, but the only feelings they tend to be sensitive to and in touch with are their own.
Nora Ephron

Beware of missing chances; otherwise it may be altogether too late some day.
Franz Liszt

Beware of monotony; it's the mother of all the deadly sins.
Edith Wharton

Beware of no man more than of yourself; we carry our worst enemies within us.
Charles Spurgeon