The ames room, in which people are seen to get small or enlarge as they move about, demonstrates that our perception of the world depends strongly on

The answer is:  the assumptions we make about the world.
This principle could be translated into two different people that give two opposite response in handling a same problem. (one succesful and one catastrophic)
One people could be influenced by optimism that make him/her believe tha the problems is not going the hurt them, while the other could be influenced by negative outlook that become self-fulfilling phropecy of his/her failure)