In the pages about the uses of "ser" and "estar" we gave some fairly confusing explanations. Please look at them again.

We use "ser" with an adjective to express a permanent or inherent quality
El azúcar es dulce

sugar is sweet

mi padre es calvo my father is bald
mis hermanas son altas my sisters are tall

We us "estar" with an adjective to express a temporary or unusual quality
Another way of saying this is: To express a quality or state seen by the speaker as subject to change or different from expected
la sopa está un poco fría

the soup is a bit cold

María está muy guapa hoy María is looking very pretty today
Hoy estoy de mal humor I am in a bad mood today

For many people these types of explanations may be correct but they may not be very helpful.

The concepts maybe more easy to understand by comparing the different meanings below.

Es un borracho

He is a drunkard

Está borracho He is drunk (at the moment)

El chico es pálido

The boy is pale (he has a naturally pale complexion)

El chico está pálido The boy is pale (he is pale at the moment because he is ill)

El hielo es frio

The ice is cold (ice is inherently cold)

Este café está frio This coffee is cold (it has gone cold)