This is the 10704th most frequent Portuguese word.
guardada
Stored; kept; saved.
The word 'guardada' is used to indicate that the object (the letter) has been stored or put away in a specific location (the drawer) in past tense.
A carta foi guardada na gaveta.
The letter was kept in the drawer.
Here, 'guardada' describes the state of an idea being kept or stored in someone's memory persistently, relating to a preserved thought or concept.
Ela sempre teve essa ideia guardada na memória.
She has always kept that idea stored in her memory.
The phrase 'guardada por todos' demonstrates how 'guardada' expresses the act of preserving or maintaining something (the promise) collectively by a group.