The First Amendment of the U.S. Constitution guarantees your right to freedom of speech. However, that freedom only relates to government persecution or prosecution related to what you say. Freedom of speech does not protect you from all consequences of your words.
If, after a long shift at the hospital, you say something rude to a patient or one of their family members, it could lead to career problems for you. Not only might that person make a complaint to your employer that results in punitive action, but they could also take their complaint to the California Board of Registered Nursing.
Unprofessional conduct or mental illness are both grounds for board review
The language that you use when you communicate with your patients could make you seem unprofessional or even unstable.
For example, using the wrong pronouns for someone could lead to allegations that you have intentionally disrespected them, which could be unprofessional conduct. A joke or a colloquial phrase that you use could have racist connotations that you do not realize. What you say could make you seem unprofessional and potentially dangerous to an entire portion of the population.
On the other hand, if you express anger, frustration or burnout with your job, that could lead to allegations that you have mental health issues. It could be particularly difficult to fight back against such allegations without help.
However, it is crucial that you take these allegations seriously, as any complaint deemed serious enough to warrant board review could potentially cost you your license. Understanding what might lead to disciplinary action can help you defend your nursing license.