They have a concept of themselves that is in many ways stranded in time at that point just before the injury to the brain. The same is true for those with mental illness, they perceive themselves to be in the state they were in before they became ill. The number one reason people with psychotic disorders do not take their medicine is poor insight into their illness. Perhaps as many as 80,000 West Virginians have schizophrenia or a bipolar disorder, half of these do not think they are ill or are unaware of many facets of their illness. Therefore, they are very unlikely to take their medication.
Most mental illnesses are chronic with exacerbations and periods of remissions.
There are very few cases of complete remission. Failure to treat psychotic episodes resulted in worsening of the mental illness, poorer response to medication, and increased overall severity of the illness. One theory is that psychosis is essentially toxic to the brain. Therefore, aggressive treatment is indicated. Those who get treated late do much worse.