The last thing is Happiness is often mixed with sadness. After moving to new home, Sadness often walked to touch the Memory Orbs, Riley's memories, and that change the happy memories into sad memories even though she didn’t mean to do that. The truth is whenever Riley go back to think about Minneapolis, although it will make her happy, it also makes her unable to feel sad because of missing. In moments Joy and Bing Bong would be forgotten and cease to exist. It seems that all hope was lost. Joy, in despair, reminisces and cries about the happy moments that she remembers, stating "I just wanted Riley to be happy." notices something interesting about the memories that Sadness inadvertently caused, realizing that when Riley was sorrowful, it signals to others that she needs help. Joy realizes that Sadness's main role in Riley's personality is to tell others when she needs help, and by preventing Riley from feeling sad, she was also preventing her from feeling true happiness, sometime sadness bring happiness. Hope comes when Bing Bong notices his rocket, and they decide to use it to return to the top, but are dismayed when it falls short every time they tried to sing louder. Bing Bong, in a moment of self-realization, starts the rocket one last time, then jumps off as it begins to fly. Joy looks back, realizing Bing Bong's act of selflessness, and Bing Bong thanks Joy for letting him be important one last time as he vanishes, forgotten. He chose to be forgotten to let Riley grow like we have to leave some happiness in the past and move on.