There is a such a thing as situational depression, that can lead to self-harm but it is also a clinically discernible mental health issue, therefor you're not "mentally healthy" at the time.

Also, bit of a tough discussion, it is IMO possible to be mentally healthy and not wish to go on living if confronted with severe life circumstances, that's why some places allow medically-assisted suicide for those terminally ill.

Not wishing to be insensitive but IMO no mentally healthy person would conclude it's better to die than to change careers. Even if that involves a change in personal financial circumstances.

I suppose someone could be a in a harder spot if their entire family life and circumstance revolved around being wealthy, ie the wife and kids will leave immediately if you stop earning good money. That's not a family circumstance I'd care to be in personally.