I started measuring my sleep this year. The data is as follows: I feel well and I can focus if I sleep for 8:00-8:30 hours. If I sleep less than 7:00-7:30 hou

I started measuring my sleep this year. The data is as follows: I feel well and I can focus if I sleep for 8:00-8:30 hours. If I sleep less than 7:00-7:30 hours per day I feel unwell and I cannot concentrate. In between 7:30-8:00 hours I can somewhat concentrate but not for too long. Sleeping longer over weekends does not work for me, since I still wake up at (usually) about the same time every day. So I still sleep about the same time every day.