Darren ducks out and returns five minutes later, carrying eight freshly strung rackets. He sets them atop my bag. He knows I want to place them in the bag myself.

I obsess about my bag. I keep it meticulously organized, and I make no apologies for this anal retentiveness. The bag is my briefcase, suitcase, toolbox, lunchbox, and palette. I need it just right, always. The bag is what I carry onto the court, and what I carry off, two moments when all my senses are extra acute, so I can feel every ounce of its weight. If someone were to slip a pair of argyle socks into my tennis bag, I’d feel it. The tennis bag is a lot like your heart—you have to know what’s in it at all times.

It’s also a question of functionality. I need my eight rackets stacked chronologically in the tennis bag, the most recently strung racket on the bottom and the least recently strung on the top, because the longer a racket sits, the more tension it loses. I always start a match with the racket strung least recently, because I know that’s the racket with the loosest tension.

My racket stringer is old school, Old World, a Czech artiste named Roman. He’s the best, and he needs to be: a string job can mean the difference in a match, and a match can mean the difference in a career, and a career can mean the difference in countless lives. When I pull a fresh racket from my bag and try to serve out a match, the string tension can be worth hundreds of thousands of dollars. Because I’m playing for my family, my charitable foundation, my school, every string is like a wire in an airplane engine. Given all that lies beyond my control, I obsess about the few things I can control, and racket tension is one such thing.