Why do emotions go away after you sleep?

When you sleep you aren't using the best qualities of your mind because your brain is resting and on sleep mode, using only your subconscious mind. Really you're half dead mentally. This is why emotions creep in while you're sleeping, whereas if you were awake you'd control those emotions and channel them logically into something more productive. When you awaken, you are at your best again with control over your mind and emotions. This is why a new emotion may come over you upon awakening. You're alert and using your emotions wisely.

The power of sleep, consolidating memory

And dumping data where needed.

Best wishes

Mars mission

Source:) studies.