Awareness.

Imagine if your memory played tricks on you. That some events in the past you suddenly remember happening. And then that people in the present are conspiring against you. And only you are fully aware of what is going on. That is psychosis - at least my experience of it.

Then imagine you can remember not remembering those events. That you have a diagnosis of Paranoid Schizophrenia. And that there is a very real possibility that reality and you have parted company. That is what it is like when you have some idea that you've gone through a bad spell.