If you think someone is depressed, here is a comprehensive site with suggestions about what to do.
If you think that someone is you, here's a good page to start on.
If you think that someone is me, go eff yourself.
No, not really. Just simulating one response you might get --- to warn you that the person you try to help might not exactly welcome it.
Untreated, depression can be fatal.
But there are remarkably effective treatment options.