I am in my mid thirties and would say I definitely do not think I am as sharp now as I was as a teenager.
That said, I am overall much happier now.
For me, mental agility has proven less important to me than a number of things. Example: I have been hit by motorists a few times (I am a cyclist.) and my left knee has really taken a beating as a result. Keeping it in good shape so that I can continue to run and bike is much more important to me than, for example, being able to quickly memorize or learn something. As I see it, mere speed at assimilating information is a luxury whereas physical mobility is a necessity for having a life worth living.
Conversely, certain things have gotten better with age: my financial wellbeing and emotional maturity both come to mind.
Although I try not to worry about the inevitable and live in the now, I am personally more concerned about the point in my life where my body will entirely preclude certain activities.
That said, I am overall much happier now.
For me, mental agility has proven less important to me than a number of things. Example: I have been hit by motorists a few times (I am a cyclist.) and my left knee has really taken a beating as a result. Keeping it in good shape so that I can continue to run and bike is much more important to me than, for example, being able to quickly memorize or learn something. As I see it, mere speed at assimilating information is a luxury whereas physical mobility is a necessity for having a life worth living.
Conversely, certain things have gotten better with age: my financial wellbeing and emotional maturity both come to mind.
Although I try not to worry about the inevitable and live in the now, I am personally more concerned about the point in my life where my body will entirely preclude certain activities.