Positive thinking leads to bad result
Gabriele Oettingen conducted an experement after which, as a reslut, she claimed that positive thinking may effects us badly in planning future and achieving success.
Experiment
Students from all over the world who liked people who lived on a great distance from them were asked about what they thought about going with those people from different countries/cities. They also were asked about how they're going to overcome these difficulties.
Result
Eventually, almost no one got into a relationship. Their "positive" dreams about how they're going to spend, for example, their next weekend with their partners gave them some kind of satisfaction of a completed task. They didn't think about facing problems with travel or finding a job, for example.
Conclusion
If you want to achieve success, don't always think negatively or neutral, but always keep in mind difficulties that you're going to deal with and necessarily think about solutions to them. Thus you'll get more benefit
