Antifragility is the idea of putting pressure on a system, or human, the system or human actually grows bigger and stronger.
Antifragile systems are all around us. One example of this is our muscular system. We go to the gym to lift weights. By doing so we are putting pressure on our system to help it grow stronger. The human body is an antifragile system.
From a psychological perspective, antifragility comes in the form of PTG, or post-traumatic growth. After we experience a stressful event, we learn and grow to become more resilient.