Positive thinking

Seth posted his thoughts on positive thinking.

[I]t's been shown over and over again that it improves performance over negative thinking.

Key question then: why do smart people engage in negative thinking? ...
The reason, I think, is that negative thinking feels good. In its own way, we believe that negative thinking works. Negative thinking feels realistic, or soothes our pain, or eases our embarrassment. Negative thinking protects us and lowers expectations.
In many ways, negative thinking is a lot more fun than positive thinking. So we do it.
If positive thinking was easy, we'd do it all the time. Compounding this difficulty is our belief that the easy thing (negative thinking) is actually appropriate, it actually works for us. The data is irrelevant. We're the exception, so we say.
Positive thinking is hard. Worth it, though.

I am not so sure that positive thinking is hard. An example would be the Endowment Effect. Sometimes, negative thinking is hard, when you have it, or already started it. Positive thinking is hard, when you don't have it yet, have not started it yet.

Both are valuable. The million-dollar question is how to strike the balance.