There was a study done where patients were told there is 40% chance of success. They liked it because of the word success. Then they are told there are 60% chance of failure they didn't like at all. Same way they were told there are 40% chance of failure. They disliked it. Then they are told there are 60% chance of success. They still were reluctant.

So it seems like human mind wants to see half empty glass and not become an optimist.