I think mental illness is starting to become a public health crisis. I know only a few people that aren't constantly stressed due to work or school. I've seen many people fall into legitimate depression and only recover after changing their environment, like quitting their job.
We use exercise to improve our bodies. Like exercise, improving your mental health takes time and conscious effort. You need to dedicate time every day for honest self-reflection, self-awareness, meditation, reading and education in the topic, etc.
There are two ways you can lose weight. Accidentally--by getting sick or stressed, for instance--and on purpose, as through concerted diet and exercise. The same can happen with personality changes. It can happen accidentally, through change of environment or mental illness like depression.
But doing it on purpose is more wholesome. Losing weight on purpose is better than losing it accidentally, even though the result is the same, because those people are healthy and the others aren't. Put another way: you shouldn't have to get sick to lose weight.
Everybody should spend some time daily on those mental health items above. It's exercise. Through it you can point your personality and mind in the direction you'd like it to go, and with hard work and patience you'll get there. As your mind gets healthier the less likely you are to become mentally ill. You'll avoid common issues like depression, substance abuse, anxiety and eating disorders.
It's said that half of adults experience depression at least once in their life. I bet it's more like 90%. It's like the flu. Pervasive, transmissible and contagious, with most victims recovering quickly, but a small percentage experiencing fatal cases. Now we have flu shots at every Walgreens.
It's time to do the same for mental health. And until we have more public programs to support mental health, you'll have to take it into your own hands.