Every August, without fail, something shifts in the air. The light changes. The mornings get a hint of crispness that wasn’t there in July. My body feels it before my brain registers it — a subtle signal that the lazy, sweaty, endless-seeming summer is slowly winding down. And for years, I ignored that signal. I’d ride summer right into September, then wonder why I spent the first three weeks of fall fighting a sore throat and crushing fatigue. It took my track coach back in college — a woman who’d trained Olympians and had zero patience for my excuses —…