A student of a foreign language cannot merely practice in his or her head without speaking and writing. If the student waits to come across a native speaker, the student will sound ridiculous and ultimately be disappointed by his or her inability to verbally connect to the other person. This is why any student of a foreign language takes classes: because the classes force them to speak and write—to exercise their abilities.
Similarly, students of English must exercise their abilities to recognize symbols, dissect dialogue, and create believable scenes and characters. This must occur before they are able to write works worth reading. This is true for college graduates, as well as autodidacts: all aspiring writers must practice writing.