"You have so much to live for."
"Why can't you just be happy?"
Those are just a few of the things that people with mental illness are told on a regular basis. Things that, in many cases, just make the person suffering feel guilt. Guilt that results in ruminating and self loathing, which makes their situation that much worse.
What people don't realize is that, as I've said so many times before, mental illness is a chronic disease. It can be managed with medicine and therapy which in the best cases can keep people stable, but finding that perfect combination of treatment can take years; years that some people can't survive because they don't have a support system.
It's a disease that people who suffer have to spend countless days fighting. Days where they have to force themselves out of bed, force themselves to eat, force themselves to leave the house. Force themselves to get through another day.
If you love someone who suffers from a mental illness, stop telling them to "just snap out of it" and try listening. Tell them that you are there for them. If they need space, respect that while checking in and making sure that they stay safe. Get them involved in a program or group that allows them to talk to someone who "gets it." But most of all, be compassionate and empathetic because mental illness is a disease, not a state of mind.