The brain goes through a lot over the course of an average lifetime. It is a remarkably adaptable organ capable of repairing and rerouting connections over the course of a human lifetime. This also means that, when properly care for and trained, it can resist quite a lot of curveballs life can throw at it.
The brain is a very resilient organ. Even in the face of all but the most extensive damage, the brain can create new connections and maintain functionality, and damaged connections can be repaired. It retains the same level of connectivity even when parts of an existing pathway are damaged, and are only impaired or lost when the damage is complete.
In these cases, such as those found in traumatic brain injury, the damage is often so severe that it compromises many mental faculties, slowing down the ability of the brain to repair the connections. The proper training and conditioning, however, would allow the brain to speed up the process of self-restoration, by guiding it to the connections that have been lost or compromised.
Indeed, it is this ability to create new connections and maintain old ones that have sparked interest in utilizing brain resilience and plasticity for rehabilitative medicine. Findings have consistently shown that an active, engaged brain is a very resilient one. Mental activity has been found to reduce the rigors of stress and prevent or counteract the onset of degenerative mental conditions come old age.