High or prolonged doses of any of these behaviors or substances aren’t sustainable or healthy (spend too much time in cold water, and you’re gonna get hypothermia). But in short bursts, the little bit of irritation that these stressors cause is just enough to knock you out of comfortable homeostasis and activate a variety of cellular mechanisms and signaling pathways that promote stress resilience, repair cellular damage (via processes like autophagy), repair DNA, combat oxidative stress, produce new mitochondria, reduce inflammation, support elimination of toxins, improve blood sugar regulation, reduce risk of cancer, and more, explains Rountree.