An intelligent woman is better than a beautiful one

After all, a beautiful woman without a mind of her own leaves her lover with no resource after he has physically enjoyed her chasms. An ugly woman of brilliant intelligence makes a man fall so much in love that she leaves him feeling no lack.
Ask a beautiful woman who is not very intelligent if she would give some small part of her beauty for a little more intelligence. If she is frank she will say that she is satisfied and what she has. Why is she satisfied? Because, having only a little, she can have no notion of the intelligence she lack. Ask an ugly but inteligent woman if she would change places with the other. She will answer no. Why? Because, having a great deal of intelligence, she knows that it serves her for everything.

Giacomo Casanova - History of my life (3, 3)

Beauty doth varnish age

BIRON:

A withered hermit, fivescore winters worn,
Might shake off fifty looking in her eye.
Beauty doth varnish age, as if new born,
And gives the crutch the cradle's infancy.
Oh, 'tis the sun that maketh all things shine!

William Shakespeare - Love's Labour's Lost (4.3)

Beauty is in the eye of the beholder

PRINCESS:

Good Lord Boyet, my beauty, though but mean,
Needs not the painted flourish of your praise.
Beauty is bought by judgement of the eye,
Not uttered by base sale of chapmen's tongues.

William Shakespeare - Love's Labour's Lost (2.1)

Don't mix friendship with love

CLAUDIO:

Friendship is constant in all other things
Save in the office and affairs of love.
Therefore all hearts in love use their own tongues,
Let every eye negotiate for itself
And trust no agent, for beauty is a witch
Against whose charms faith melteth into blood.

William Shakespeare - Much ado about nothing