During the day one can become more and more awake because of activities that connect to the higher sense of self, especially hen one is a practitioner of self-realization: meditation, all types of yoga, doing sports, singing, dancing, connecting with others, being in nature, breathworks, rituals, etc.
At the end of the day, one can feel more connected to his/her eternal self and more detached from the preoccupations of his/her ego. There is a feeling of more perspective in life and positivity about engaging with it.
In the evening there is a feeling that the day shouldn't end and continue with this heightened sens of self. Eventually, everyone gets tired and we need go to sleep. The next day, when we wake up again, it seems like there was a reset of the mind and a disconnection between the ego and the realized self. What happened the day before was forgotten and one doesn't feel the same about it anymore like the moment before going to sleep. One can rationalize about all the things that were understood, remember how one felt the day before and what the goals or plans were for the next day, but the feeling of conviction and determination is gone.
There is the phenomenon of sleep inertia, from Wikipedia:
Sleep inertia is a physiological state of impaired cognitive and sensory-motor performance that is present immediately after awakening. It persists during the transition of sleep to wakefulness, where an individual will experience feelings of drowsiness, disorientation and a decline in motor dexterity. Impairment from sleep inertia may take several hours to dissipate. In the majority of cases, morning sleep inertia is experienced for 15 to 30 minutes after waking.
Now that there is a neurological/biological identifier for the phenomenon, I would like to have some philosophical insight on this, because I believe there could be more understanding and guidance for the direct experience of this phenomenon.
So why is the cycle of sleep influencing the sense of self and how does this link with different philosophical discourses?