I try to aim for 6-7 hours sleep at night, but I sometimes struggle to sleep during the week as I know I’m up early for work the next morning which of course means the harder I try to sleep, the more I stay awake and I’m even more knackered the next day.
I also went through a bad cycle of sleeping for 3/4 hours when I got in from work in the early evening so when I went to bed at midnight I was wide awake. Try to avoid that now.