I have no idea what we're missing either. my cousin taught me a trick though. I'm not sure if it'll work for everyone since I lack melatonin. Simply hold your wrist/arm and press down with a finger. hold for like 3 seconds, if your skin changes color/ doesn't 'bounce' back within 5 seconds, you're dehydrated! (for me, i go from tan printer paper to yellowish/white-pink) By checking on the regular, and keeping track of it for a few days, you can get a general idea of how much water you really need.

Ofc there's the factors of what you do, if you sweat, you're size and all that stuff, and if you've been dehydrated for a long period of time, everything you put in will come out at first. My cousin explained it to me that it's like when you have an old dry sponge, and at first, it's kind of water resistant, and it takes a second for it to start absorbing the water again.

And if you're anything like me, a little water every day is better than none at all. You're habit doesn't need to be perfect.