How come whenever you wake up super happy, you are super depressed by the end of the day?

Being excessively sad appears to be a reoccurring thing after a memorable moment. Now it's an expectation that whenever I start off super happy on a very good day, there's a depression that comes afterwards. I recently had a conversation with a friend/co-worker about these events only to realize that I'm not alone. Perhaps the reasoning behind this process has to do with knowing that the joyful moment has ended or maybe the brain is so overwhelmed by these positive notions that it is automatically shut down. It's true emotions shape the perception of how we see the world. It's just fascinating how one perception can drastically change in an instant. If there is a scientific reasoning or logical explanation, it would be an interesting thing to learn about. What do you think causes these notions and what is a time you experienced them?
How come whenever you wake up super happy, you are super depressed by the end of the day?
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