Research on the planning fallacy indicates that we tend to when making predictions about ourselves and we tend to when making predictions about other people.

be excessively optimistic, be realistic
   This is a practice in which expectations about how much time will be expected to finish a future undertaking show a positive thinking inclination and belittle the time required.
    This phenomenon happens paying little mind to the person's information that past undertakings of a comparative sort have taken more time to finish than by and large arranged. The predisposition just influences expectations about one's own undertakings; when outside onlookers foresee assignment consummation times, they demonstrate a negative inclination, overestimating the time required

The declaration of sentiments