Bollocks, honestly.
When I was 23, I had a girlfriend turning 20. At her birthday party, her friends were talking earnestly about how "depressing" [sic] it was to turn 20. Then one of them pointed at me and said with obvious consolation, "well, at least we're not old like Richard!". When I turned 28 I felt depressed about being old. I went to sit by the river with a friend, and one of his friends who came too had just turned 23. I sighed internally, "oh to be young again, to be just 23!". Shortly after I went to my great aunt's birthday party. She was turning 85. She asked me how old I was. When I told her, she said, "28! A mere spring chicken!".
From that point on, I decided never to care about how old I was. For 95% of your life, possibly more, there is someone who thinks you are old, and someone who thinks you are young. Don't think about it, work on the assumption you're young enough to do whatever you want, and give it a shot. You're really only old when you're dead.