Question

You just broke up with someone you had been dating for a few months. you are surprised at how upset you are over the breakup, given that the relationship was not that serious. this is an example of how people have difficulty predicting the

Answer 1

I believe the answer is: intensity of their future emotions 
the intensity of their future emotions tend to be influenced by the combinations of factors such as memories, habbit, and  events that we experience in the future.
Since most people are not directly aware of the existence of these factors, it is really hard for most people to predict the intensity of their future emotions.