At the lower level, it could include your attachment to a sports team. The sports team performs well, you feel happy; the sports team loses, you feel disappointed.
Then it extends to possessions such as money. You make money, you feel happy; you lose money, you feel unhappy.
Then it extends to relationships. Your son is doing good, you feel happy; your son performs poorly in studies, you feel sad.
All of the above disappointments stem from our attachment to our identity or ego. ‘My’ team lost, ‘I’ lost money, ‘My’ son or daughter did not perform well. When ‘My’ and ‘I’ evaporates, disappointments and sadness disappear too.
Enjoy what you have and express gratitude but also not get too attached to your identity or ego!