Why hydration is a lever, not a vibe
What water actually does, and what mild dehydration costs you.
You are roughly 60% water by mass. It's the solvent every reaction runs in, the coolant for your temperature, the medium that carries nutrients in and waste out, and the cushion around your brain and joints. None of that is optional — which is why your body defends water balance aggressively.
The catch: thirst lags behind need. By the time you feel thirsty you're already mildly dehydrated, and the early cost shows up not as a dry mouth but as worse thinking and mood.
Thirst kicks in around the point where performance is already dipping. Don't use it as your only cue — anchor intake to a daily target and your urine color instead.
What's usually the FIRST noticeable effect of mild (1–2%) dehydration?