One discussion which always interests me is about positive thinking and whether it's a good thing. I suppose it depends on what is meant by "positive thinking", because there's a yawning chasm between remaining cheerful and optimistic when things are looking less-than-hopeful and unrealistic delusions about possibilities.
I would describe the latter as wishful thinking, which translates as somebody believing that all they have to do is wish for something, imagine it, and it will become so. A very profitable industry has grown up around this approach, because it's what people want to hear - after all, you're much less likely to sell a book which is honest and direct about life (and death), since most of us want to escape that - but in the end, avoiding reality is counter-productive.
For example, saying "I wish my home was tidy" will not make it so; we have to be prepared to look at our untidy home with wide-open eyes to see the nature of the problem and be able to address it. I would suggest that this applies no matter what the concern, but it's not a popular philosophy. Nevertheless, those who can grasp the concept are much more likely to find success; positive thinking may have played a part, but it's not what made it happen.