There are a few strategies you can use to help your relative reduce the chances of having another episode of psychosis. These include:

taking medications as prescribed
attending psychosocial programs that help with treatment and recovery
abstaining from alcohol and other substances
maintaining good physical health and adequate self-care (e.g., eating properly, getting enough sleep)
establishing a routine
reducing stress as much as possible
developing good communication and problem-solving skills to deal with unavoidable stress
having someone to talk to
developing a social support network
having stable accommodations
preserving a sense of hope
engaging in meaningful activities (e.g., studies, work or hobbies).