I feel like my best work happens in about 6 hours on most days. Beyond 6 I feel like I'm less motivated/productive, I get things done but it goes a little slow

I feel like my best work happens in about 6 hours on most days. Beyond 6 I feel like I'm less motivated/productive, I get things done but it goes a little slower. I've previously done a 9/80 schedule with every other Friday off. The 9 hour days made my personal life harder, harder to meet family obligations like pickup/dropoff. I'm cool with 5 shorter days, I would be happier and probably more productive.