[TeaDrunk]

Schizophrenia can be more or less severe. A schizophrenic with very mild symptoms, a stable life, access to food and shelter, no unhandled trauma, etc. can function and even thrive without medication. The disease can also get better with age.

Consider: you can hear voices and choose not to respond to them. You can have delusional beliefs and not act on them. There's no functional difference between talking with your mom on the phone and talking with an alien that has replaced your mom on the phone if you're willing to play along or simply acknowledge "hi schizophrenia, funny idea, that".

[wheelerof4te]

On point. Many people know that they have this problem and can act before it manifests in reality, through action.