Much of what we now do in Critical Care carries an air of urgency, a pressing need to discover and act, with priorities biased toward a reactive response. However, efficacy often depends not simply upon what we do, but rather on whether, when, and how persistently we intervene. The practice of medicine is based upon diagnosis, integration of multiple sources of information, keen judgment, and appropriate intervention. Timing may not be everything, as the well-known adage suggests, but in the intensive care unit (ICU) timing issues clearly deserve more attention than they are currently given. Successfully or not, the patient is continually attempting to adapt and re-adjust to acute illness, and this adaptive process takes time. Knowing that much of what we do carries potential for unintended harm as well as benefit, the trick is to decide whether the patient is winning or losing the adaptive struggle and whether we can help. Costs of modern ICU care is enormous and the trend line shows no encouraging sign of moderation. To sharpen our effectiveness, reduce hazard, and pare cost we must learn to time our interventions, help the patient adapt, and at times withhold treatment rather than jump in on the impulse to rescue and/or to alter the natural course of disease. Indeed, much of the progress made in our discipline has resulted both from timely intervention when called for and avoidance or moderation of hazardous treatments when not. Time-sensitive ICU therapeutics requires awareness of trends in key parameters, respect for adaptive chronobiology, level-headed evaluation of the need to intervene, and awareness of the costs of disrupting a potentially constructive natural response to illness.