Chris Hadfield said this quote

It's puzzling to me that so many self-help gurus urge people to visualize victory, and stop there. Some even insist that if you wish for good things long enough and hard enough, you'll get them - and, conversely, that if you focus on the negative, you actually invite bad things to happen. Why make yourself miserable worrying? Why waste time getting ready for disasters that may never happen? Anticipating problems and figuring out how to solve them is actually the opposite of worrying: it's productive. Likewise, coming up with a plan of action isn't a waste of time if it gives you peace of mind. While it's true that you may wind up getting ready for something that never happens, if the stages are at all high, it's worth it.