For the purposes of the movie, they shortened the octave of emotions to five and showcased three. This was rightfully so as it would have muddled the movie. But think how music would be limited without one note to play; all its harmonics would be gone. So it is with sadness. We need to experience everything to gain wisdom about it. Sadness and loss are basic to life. It's how we deal with them either enriches or destroys our lives.
What encompasses all emotions is truth, especially our personal truth. I am constantly dealing with patients who have "gotten rid of" their bad memories. Their core memories are contaminated with the hurt and loss of an event and color particular beliefs. The act of avoiding and denial change a person from who they are supposed to be, to a fearful, protecting shell of themselves. They then hypnotize themselves into believing they can't deal with that issue nor anything slightly resembling it. They "become" someone else.
Most therapies are designed to access those memories and have the person acknowledge the truth of the experience, freeing the trapped energy. A witness is generally required for this to debrief the lost soul. Riley had her parents. It makes the person feel connected and grounded back in reality. A wake-up in Buddhist terms. Then when reflected on, the events are not re-lived, they are all seen more objectively which changes them with the change in perspective. The task is to get the person to believe in themselves again. They can handle it. They may need help knowing how to do it because there was a breakdown of basic needs somehow but inside are the resources for growth. They just need to be taught.
People who've gained their wisdom credit from loss and grief talk about it conceptually as being Grateful. It has a spiritual connectedness to it now. They know there was something important lost but have come to understand how precious it was that they were able to experience the person at all, or the loss helped them have compassion and grow as a human, or some other critical aspect of life is now understood. It could not have happen without that realization. And in this case, the "make real" is the truth of sadness. The joy aspect of Riley finally realized this and let her reconnect with life.