Keep working. Most modern jobs involve multi-layered thinking, problem-solving, and socializing, all of which are good exercises for the brain.
Seek out new ideas and people. Get out of your thinking comfort zone and search for new ideas and people that rattle established brain patterns and challenge you to think in new ways.
Breathe. Like the heart, the brain needs oxygen and blood flow. The current star in brain science research is exercise. So get up and move around.
