You could say that age is what you make of it ;-))

My daughter was more adult at the age of 2 than I was as her mum. Roughly speaking, it stayed that way ;-)) And she probably got that from me: I felt 35 at 15, felt 35 at 20, felt 35 at 35 and still feel 35 at almost 60. On good days, I still look almost like that ;-))

Maturity is a very individual thing and depends on many factors; the respective environment is probably the most important influence and the degree of responsibility you are allowed or required to bear. It seems important to me to retain a certain childlike light-heartedness. It can save us when things get really bad...