I have Fitbit's HR version & it tracks my sleep. On days that I'm feeling mentally foggy, I can generally attribute it to oversleeping. I think my optimum is a

I have Fitbit's HR version & it tracks my sleep. On days that I'm feeling mentally foggy, I can generally attribute it to oversleeping. I think my optimum is about 7.5hrs. If I sleep for 9-9.5, it takes me a lot longer to "wake up" throughout the day. Try & work out what your optimum is as it's different for everyone. Also, I've tried to stop drinking caffeinated drinks after 3pm & that's helped. I'm trying to not be looking at any screens an hour before bed, but that one is proving to be a little more difficult to actually do :)