A neurosis is a mental disorder that is used to show mental illness that involves an obsession or a phobia of some type. There are neurosis quotes that reveal that a little bit can be motivating while a lot can be debilitating. If you have a neurosis then this is a mild mental disorder that may not affect some aspects of your lives, but your fear or obsession on something is excessive and is not rational. Neurosis can be treated and it usually does not require inpatient treatment, but in severe cases a neurosis can turn into a serious mental illness that must be treated immediately. Someone who suffers from spider neurosis may have an irrational fear that spiders will suddenly appear, even though they know in their mind that this will not actually happen.