The best thing to do is to set process goals rather than outcome goals. 

In other words, hope for the things you can control, anticipate the things you can't

That's straight out of the book of Scott Adams, right?

http://pandawhale.com/post/43857/dilbert-creator-scott-adams-on-why-big-goals-are-for-losers-fast-company

Btw this video from Eric Barker's article is excellent.

Why Thinking Positive Fails, according to Oliver Burkeman:

There’s one specific problem that keeps cropping up again and again, and that is this idea that when you try to control your thoughts or emotions with the will, consciously, it often ends up backfiring and bringing about the exact opposite. And research shows that same pattern occurring over and over; people who try not to feel grief after bereavement take longer to recover from grief. There’s a great one about how people who are told not to feel aroused by looking at erotic pictures by skin conductivity measurements are shown to become more aroused than people who weren’t given that instruction. People with low self-esteem feel worse when they repeat things like “I’m a lovable person” to themselves because doing that provokes them to generate counter arguments.

Now watch the video: