My three kids are old enough to babysit themselves so my wife and I can go out when we want. So don't be depress about a thing. Someone told me that it can make you look and feel 10 years younger. You are afraid that you must become like some person or people you know who are a particular age when you are that age. Life doesn't come to an end until, er, it comes to an end.
Advertising has a lot to do with our age stereotypes, too.
Marketeers segment our society into different age groups, and it is unfortunate. One thing we should all get used to is people doing things at older ages than they have in the past, e.g. changing careers, having children, whatever. People are living longer and healthier, and the trend will continue. A person who is 50 years old could completely change careers now and still put in 20 or more years in the new field. As far as physical fitness goes, while it does get harder to stay in shape as you get older, it's not THAT hard.