I know many older folks (> 60) who are still vibrant and have curiosity about life. Unfortunately I do tend to agree that a certain rigidity of mind sets in at some point, and it becomes somewhat more difficult to rearrange your neurons to adapt to new ideas. It doesn't mean you cannot accomplish things, but just as it is sometimes important to realize you lack experience when young, it seems important to recognize the changes in your mind as you grow older, and accept them with a degree of grace and a willingness to acknowledge the differences.