I'm 55--I definitely think this is old----even though I workout like a 20-something still and move pain-free and still have my natural dark hair (not grey yet).
I don't feel old and in my head I think of myself as much younger---like I'll say something to my husband about the new neighbors are 'some old couple' when in reality they could be our age

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I don't think you need to worry about what is 'considered'. You stay young if you stay active and engaged and don't tell yourself in your head that you are old. Read, engage, have friends of different ages. I'm proud our 30-something neighbors consider us good friends and invite us over for dinners/happy hours. We have friends that span all ages.
I am almost empty nest and love to chat and hear from my college son and his friends. I take cues from my 17-year old--he introduces me to his music and different tastes.
My dad was very much like this and attracted people of all ages because he was funny and kept up (even outpaced younger ppl) with the latest technology. He also was interested in what people are age were doing. My mom and dad looked and moved like people 20-years younger...when I was out with my dad people thought he was a boyfriend (yuck). They thought my parents were my kids' parents when they took the grandkids out alone.
Just live your life. So many really important people didn't invent things or start certain careers until 50. Just keep going...