How can you tell the difference between your instinct & paranoia?

Can be tough: Instinctive wariness is an important tool for self-preservation. Paranoia is excessive fear beyond what is reasonable for the situation or based on faulty logic, e.g., all strangers are aliens. Being cautious makes sense in some settings; persistent, excessive worry about safety may be a sign something about you is not working right. That's when talking to a professional can be of real value.