Recently I've been thinking about expectation. I remember working with some management consultants once and their favourite turn of phrase was: You have to manage expectations.
They kept saying this. Practically it meant they needed to know what could go wrong, allowing them to manage the situation should it happen.
Recently on British terrestrial television there was a popular psychology program and they illustrated how the expectation of reward affects children; and indeed adults. Three groups of children were asked to paint; one group was left to paint, one after a brief period was given a surprise reward for their work and the third group: were told right from the start there would be a reward for painting.