Saudade
a longing, emptiness, depressed feeling after something was finally done.
Finished your high school?
Finished your military service?
Finished a big project?
After getting your degree?
Individual tends to hang onto that little bit of feeling and finds it hard to get over it, why? It was sweet, bitter, and remarkable. Those events might play an important part in one's personality development and sense of value.
Why do we miss the past so much?
After some sort of huge event, people find it hard to move on.
They clinged to it.
They talked about it.
They wanted everyone to miss that too.
They emotionally related to it so much.
Why?
Because reality is harsh.

Everyone moved on.
Your next tasks are stressing you out, causes you to regress.
You climbed so high in previous project and you don't want to back to square one for new things.
Fame
Glory
Ego
Pride.
And memories.

Just like Olympics athletes finished their matches which they have been practiced for years
Just like an old folk sitting on the park bench whilst sharing his world war experiences.
Just like a normal teenager who finished a TV series.
Just like a group of students finished their performance for their graduation prom night.

Saudade. I used to not knowing how to describe it.

Memories are good, but you can't be the only one memorizes it.