There are three types of waves in our body and they are defined by six high-lows. Their wavelength differed but they all propagate together.
Hunger-Thirst are bodily waves and in a day they attain their both peaks. Happiness-Sadness are mental waves and everyday they too attain their peaks may not be significant to even get noticed. Life and Death are waves of soul, each day you wake up life begins and attains its peak, actually you woke up before that but kept lying in bed dreaming happens during this phase. Each day you sleep and another peak is attained after 2-3 hours when you become completely unconscious ie Death like.
You are not part of any of these but the watcher in you keeps watching them happening on body, that is why when you had great sleep who notices it? You are actually watcher and your attachment with body happened in adolescent age and is temporary in nature.