I turn 50 in a few months myself. I look at age this way, I am like wine, I just get better with time. If turning 50 is anything like the past 49 years, I am not worried about it. I have enjoyed the past 49, and look forward, and don't think turning 50 will be any different. It might also be I don't really celebrate my birthday like I used to, usually a good meal with the family, and a movie, some quiet time with the wife, and I am good. I am happy where I have been, learned more than I thought I would, and things that used to bother me don't anymore.
It might also be because 7 years ago I went in for a simple physical. Had not been to the Doctor in years, wife insisted I go. I ended up in a cardiac care unit for 2 days. I remember looking around the room, I was the youngest one in there, most folks were in their 70's and more. I didn't do much about the medical problem until about 3 months ago, was back in for a checkup and in cardiac care for the night. I decided it was time to do something about it, bought a bicycle and have lived everyday like it is the last. I hope the next 40 years will be just as fun as the last 49 have, I would not want to repeat them, maybe change a few things if I did it again, but am satisfied where I am, and happy with what life has given me.