To boost your brain, teach a continuing education class. In addition to the joy that comes with sharing your life wisdom, teaching helps strengthen mental function through reading, self-learning, and lecturing. Teaching is also a great way for you to learn new things (“While we teach, we learn,” said the great Roman philosopher Seneca). Plus, teaching can provide a useful social outlet and feeling of purpose. Everyone is adept at something, so choose your specialty, approach a local continuing education program, and improve the world with your knowledge. You don’t need a teaching degree, just experience.