i found that when i slept for exactly six hours, my body and mind woke up rested and ready for the day. however, if i did not rise then and decided to sleep another hour, i had dreams and awoke feeling tired. forty-five years old and i am still learning how to sleep and when to rise. wow.
there is no work you cannot do when you are rested. so take your rest if you can, and do not be so busy for so long.