Fitzgerald isn't simply saying that love varies from person to person—he's suggesting something more unsettling: that even with the *same person*, you cannot step into the same emotional current twice. Time reshapes us both, and yesterday's tenderness becomes impossible to recreate, only to be replaced by something altogether different. This matters because it releases us from the exhausting fantasy that we're chasing some fixed ideal, and instead asks us to honor each love for its particular texture and timing. When you find yourself nostalgic for how things felt in an old relationship, remember that you're not mourning a loss so much as acknowledging that you and they have both become different people—and that's not tragedy, it's the price and privilege of being alive.