N2L, I am exactly the same as you. I have tried the whole 'positive thinking' and it has let me down so many times that I just don't believe in it any more.
I also know that there is nothing we can do to change a situation that is out of our hands. I get very emotional/depressed when I build myself up on positive thinking that doesn't follow through. So I just don't do it anymore, it seems to help a lot with how I feel when things are falling apart.

It may sound very pessimistic, but if it's how you cope then so be it. I only allow myself positive thinking in a situation where I know the outcome is in my favour