Expectations

It really makes me wonder why in this world is there always a mismatch of expectations between two people. Your expectations out of your job is different from the one your boss has from you, your expectations from your partner / friends is different from what they have from you , finally the stock markets run on the premise of expectations mismatch . No matter how best one tries to make the communication transperant, there is always this mismatch between two people. It sounds irritating and uncomfortable listening from your superiors and telling your subordinates that you have ' met expectations', 'exceeded expectations', 'above / below expectations'....and the list goes on. This reminds me of a famous quotes :
"Unhappiness is best defined as the difference between our talents and our expectations" - Edward De Bono
It is quite surprising to realise the fact that there is only a small portion in this whole world where expectations expected are matched ( that's a rarity). Is it correct to not to expect anything after having slogged to complete a work or is it correct to expect more than you deserve or more than you can get from some person or something over a period of time ( can be short or long) ? It always continues to confuse me!