A while ago, I read a post on a blog of a mother with cancer how she disliked some ways of using the word fighting. The crux of the matter was that you didn't beat cancer based on how hard you faught, some will die, some will survive and to consider those that died to have somehow not faught as hard is wrong. Now there may be some fuzziness around the edges with that, I've definitely seen new articles announcing research about the good effects of positive thinking, but it's still a pretty fair statement.
Now, here I am, feeling like really in the 8 months that I've been treated for depression that I'm really still very unwell, but with mental health issues I rather suspect that fighting does make a difference, though ironically the illness may take away your ability to fight. So does the fact that I'm here now mean I've not been fighting? I think not, an obvious consequence of depression is suicide, I'm still here, I think this means I'm fighting.
When people are fighting physical diseases we seek to encourage them, do we believe that our encouragement will cure them? It's usually something we just do, it just is what one does when someone is ill, subconciously I think we're actually trying to prevent depression, which as it turns out is an entirely reasonable thing to, not just because we want to avoid that suffering, but people with depression do have a reduced life expectancy that isn't entirely accounted for by suicide.