The benefits of meditation are well-documented. A regular practice can also help you notice the subtle changes that signal the onset of episodes of mood change, anxiety, or psychosis, enabling interventions worked out in advance with a professional to head off more serious episodes.
Nothing keeps away the physical health challenges that come with mental illness like being in shape. It'll help your mood, too. And it's easy. Just get out and move around.
While the independence offered by competitive employment is an important goal in treating mental illness, any disciplined activity that keeps the mind and body engaged and committed can only help you return to health and productivity.