This can seem a puzzling phenomenon if you view altruism as a drain on your own resources. From this point of view, our own losses should motivate us to conserve energy and hold on to whatever resources we have left. Why would suffering make people so eager to be of service? The answer seems to lie in something we’ve already considered: how caring creates courage and hope. As we’ve seen, helping others can transform fear into bravery, and powerlessness into optimism.
When life is most stressful, this benefit of tending and befriending is even more crucial to our survival. The instinct to help when we, ourselves, are struggling plays an important role in preventing a defeat response. The defeat response is a biologically hardwired response to repeated victimization that leads to loss of appetite, social isolation, depression, and even suicide. Its main effect is to make you withdraw. You lose motivation, hope, and the desire to connect with others. It becomes impossible to see meaning in your life, or to imagine any action you could take that would improve the situation.
— The Upside of Stress (Kelly McGonigal), Loc. 2435–43