Are you going to perfectly hit 64 or 91 ounces every single day? Heck no. And that’s perfectly fine. Some days you’ll drink a lot, some days less, and your body will adjust. The goal is progress, not perfection.
If you feel thirsty, you’re already a little dehydrated—so drink up! If you’re not thirsty, you’re probably okay. Trust yourself. You’re smarter than a one-size-fits-all rule.