Focus, strategy, logic and creativity are just a few of the mental muscles you should be exercising more regularly.
The more regularly you pick up a new skill, study a new subject, or dig deeper into any topic, the stronger your mind becomes. Try to pick up one new thing every week, then continue working on it as you learn new things.
Don’t stop looking for answers. If something doesn’t make sense to you, look for ways to expand your knowledge so that you do understand it.