I turned 50 last fall and for me, it was a great milestone. Whenever I walk into a room, people think, "this guy knows his stuff." Of course, this is because of all the screwing up I did up to that point. The 20 year old me was not something I would want to be around for long.
Fifty doesn't have to be old, and I think anything that doesn't move or work dies. Pretty rare day I miss my workout in the gym. I run, climb mountains and scuba dive. Best of all is my (rather younger) Sweetheart can keep up to me. I still work part time to get me away from the house, mostly consulting jobs, as it is important to be useful.
We eat well, since keeping your health at my age is paramount. We are not food nazis, but we eat lots of veggies and rice and not a lot of meat. Not that we are veggietarians, it's just what we prefer, although a grain-fed, organic Canada Prime steak is a nice treat.
Knowing the world really isn't a dangerous place, and that the vast majority of humans are nice is a great benefit of being old, as is casting off the propaganda governments habitually spew.