Context

A symbol without context is just an object. Context is the material around an object (within a text or from outside the text) which imbues it with the impressions beyond its first literal reading. To give an example, without context, "the curtains were blue," has nothing to bare beyond its apparent literal meaning: the curtains were blue: However, consider the phrase again, this time with a minimal amount of context suffixed: "the curtains were blue, like the sky I used to look up at: god, I miss the sky." In this example, the blueness becomes a facsimile of the sky, which is in turn associated with freedom and hope; and the absence of the sky then makes the curtains become an antithetical symbol of the sky and its impressions. When the curtains are simply blue, no context given, there is no ability to read a deeper understanding into the text, because the text is only one layer thick, but by contextualizing the curtains being blue so that it associates to another thing, the blueness of the curtains becomes symbolically significant, in the case of the example they become a symbol of confinement and despair. By supplying context, the curtains stop being just blue and start being blue in service of a deeper symbolic meaning.

The relationship between context and symbols is what makes it so difficult to explain a symbol or concretely pin down precisely what a symbol means across all its usages because given the proper framework anything can mean anything; and, because the context of outside a text might change from culture to culture, or even person to person, the symbol will also change with the context even as it relates the same object within the same textual context. That's not to say that symbols are meaningless, only that their meaning is derived from the context around them, and that given a specific context, an object typically used as a symbol of hope or luck or fertility or chaos can not only be brought to represent the opposite concept but can even be tied to an unrelated orthogonal concept.

That being said, the more often an object is contextualized as a specific symbol, the easier it becomes for an audience to accept the impressions the symbol is operating from. So, the more often an object is used as a symbol for a specific impression (or antithetical impression), the less work the author needs to put into the framework of their text because the audience would have likely been exposed to the symbol before outside the text itself: but symbols with strange object/impression pairings tend to leave more lasting impressions; and some texts create entirely new objects and impressions which need their relationship thoroughly established. to create meaning for the audience.