It is not just for those that are young in years. Anyone can have their youth at any age. It is actually just a matter of how you feel. I mean there are days that I feel like I've lived more than a century and then there are days that I feel as if I were still in my teens and have the energy to match.
While growing up means gaining responsibilities, some of which you never imagined it does not have to mean losing the enjoyment of youth. Actually it can sometimes mean that you get to enjoy things that you were never able to during your younger years because of a lack of money or simply not being allowed to do them.
Children keep you young even as they test the level of your endurance. It can be tiring to spend the day running with them but it makes it easier for you to sleep at night, and you awake feeling refreshed. Keeping youth is not about keeping your youthful figure (though it is a bonus) but about living life freely and following your dreams instead of someone else's dreams for you.
Here's hoping that youth finds you at any age.