It is possible that you have a friend or relative who has an irrational fear, or phobia. Common phobias include mysophobia (fear of germs), arachnophobia (fear of spiders), and cynophobia (fear of dogs). You may be able to see how classical conditioning would play a role in developing those phobias. For instance, an individual might have been bit by a dog and developed the conditioned response to fear all dogs because of the fear instilled by the first dog bite. Classical conditioning explains how many phobias develop, but remember that there are other examples that seem to have started from childhood instead of classical conditioning.
In the following video, a woman claims to have been deathly afraid of clowns ever since she can remember. She suffers from coulrophobia and her anxiety causes severe panic attacks.
This woman admits that she will not go to the circus and avoids any interactions with her fear. This is an example of negative reinforcement, in which she removes the stimulus of anxiety, which makes her more likely to avoid being in the presence of a clown. By using negative reinforcement, this woman was, and many other people who suffer from phobias are operantly conditioning themselves to enable their phobias to continue and influence their daily life. By facing fears and attending therapy sessions, one may be able to eliminate their phobia, but many people continue to enable their life of fear through negative reinforcement.