A 60-year-old man on ICU is being treated for septic shock. He has received 40 mL/kg of balanced crystalloid over 6 hours. MAP remains 58 mmHg on noradrenaline 0.2 mcg/kg/min. CVP is 14 mmHg. A PLR test shows a 5% increase in stroke volume. The team considers whether to give more fluid. What principle should guide further fluid management?