Energy

How come some people over 30 have so much energy and love for life , as if they are energetic and vibrant kids , no one (wether parents or others ) stole or put down thier energy , thus they still have it,many interests , many things to talk about . I know a 23 year old who is also very energetic, when she goes to the gym she stays like 5 hours and she's full of life and full of feelings . I know an 80 year old who talks nonstop and still holds on to interests in life , and then there are those who are young but not so energetic and interested in life . I come inbetween , I do have energy but not always and I do LOVE life ,and my career ,so put all my effort in the things I love .