8 hours of sleep is about the optimal amount of sleep that people need to function in the day.
Some people only get 7 hours of sleep, some people get 8 hours of sleep and some people may need to sleep 10 hours per day depending on how tired they are.
I sometimes sleep 8 hours per day such as on the workdays and then on the weekends I will sleep 10 hours per day or sometimes longer depending on how lazy I'm feeling.
I find that most times for me 8 hours of sleep per night is enough for my body and not too much and I wake up feeling fully rested and ready for the day.
You should sleep as much as you need to for your health and to feel energized and refreshed the next day.
If you sleep 8 hours and still feel a bit tired the next day then you might need to sleep another 30 minutes to an hour.
Everyone is different and requires different amounts of sleep to function properly.