One of the most important things a person with mental illness must be able to do is speak their mind. Without the chance to say what they are feeling, they really have little chance to recover from their symptoms. When an individual keeps everything bottled up it usually means that they make little progress. The same can be said for most people in normal everyday life.
The next best thing for a person with an illness is to have someone who actually listens to what they say. Most of the time this is done on a professional level. But in all honesty it can be on a friend and family basis as well. It might sound simple but it can make all the difference in the world.
When I think back to all the people who played a role in my recovery, it means the world to me that they were willing to listen. They may have not always agreed with me, but they tried to understand. That goes a long way for a person who is trying to get well.