Agree with mcem, lilygran and earlier posters - you certainly are speaking for me Silverfish, at any stage of my life.
I still felt middle aged in my 50's Lilygran, but now in my mid 60's, I accept I'm part of an older generation. I suspect that longer life spans, and much improved diet/health care, means that people in their 60's and 70's are fitter than previous generations were in those age groups.
Finding the right term to name an age group - I prefer adolescent to teen, but how long is adolescence these days. I used to think it ended around 18, when young people could vote, and get married without parental consent. That still feels about right to me, but given how many adult children are still living with parents, or in shared houses, I wonder if adolescence has been extended. If so, maybe that's fair also, because that generation will be working till their 90's the way pension provision is being changed.