What are these expectations ?

Is it a word ? a feeling or a desire? Through the pace of life, each one of us has some expectations a child expects love and support from parents, An adult expects happiness from their work, old people expect to live peacefully in their end time, but do this expectation achieve our goals ? why do we expect? Do expectations kills happiness? I have always asked these questions but till now I didn't get the answer I am finding. why these expectations are made? who made them? Do people who expect less are happy in their lives? or are the people who expect more are happy? we don't know !!