over-expectation       
noun [ U ] (also overexpectation) uk/ˌəʊ.vər.ek.spekˈteɪ.ʃən/ us/ˌoʊ.vɚ.ek.spekˈteɪ.ʃən/
 期盼过高;过于期盼
the problem of expecting more good things to happen in the future than are likely to happen
  Before the match, the team manager had warned them against over-expectation. 赛前,球队经理曾警告过他们不要抱太大期望。 
 This unhappiness results from overexpectation, from the belief that we can be positive, happy, and motivated all the time.
 - More examples
 - With any new young talent in the sport, the danger is over-expectation.
 - They were left understaffed as a result of overexpectation of support from volunteers.
 - They cautioned against overexpectation before the talks began.