I'm sure that this is a common phrase, but one of my friends gave this advice to me:

"Their perception is your reality."

He was talking about management, and maintaining a good image to your employees, but the phrase applies to everything.

People's perception was that Toyota had some terrible electrical problems, and the news media, being a for-profit endeavor, ran with it.

So Toyota's perceived problems became reality, and we needed to devote 10 months of the brightest engineering minds in the world to change that.

Unfortunately, that's how things work.