The experience you described, where someone knows that their belief or fear is irrational or unrealistic but still feels strongly compelled by it, is often referred to as a "paradoxical delusion" or "insightful paranoia."
In a traditional delusion, a person genuinely believes in something that is not grounded in reality, and they might not be aware of its irrationality. However, in a paradoxical delusion, the individual recognizes, at least to some extent, that their belief is irrational or not based on evidence, yet they cannot shake the accompanying intense fear or anxiety.
It's important to note that while some people might experience paradoxical delusions, this does not mean they are entirely immune to delusional thinking. The distinction between a paradoxical delusion and a traditional delusion lies in the person's level of insight into the irrationality of their beliefs.
Experiencing paradoxical delusions or insightful paranoia can be distressing and impact a person's daily life. In such cases, it is essential for the individual to seek professional help from mental health experts, such as psychiatrists or psychologists, who can provide appropriate assessment, support, and treatment. Cognitive-behavioral therapy and other evidence-based therapies can be effective in helping individuals manage and cope with such experiences.