How do you see turning 50? Or if you have how is it?

I am turning 50 soon. The other day I woke up in bed with a panic attack. I realized now I am officially “aged” from herein on all I have to look forward to is, growing older. I saw passageways of doors closing, opportunities vanishing and unrequited dreams of study disappear into thin air.
I had so many plans and life got in the way, but also life issues. It seem then I will never conclude my studies, it is too late, I will not do lots of things I always felt there was time for. I also don’t look like 50 by any stretch of the imagination so often I am misunderstood, as I have settled into the “grumpy old woman” syndrome quite well! People just call me grumpy instead! With aging comes gifts yes, like saying no because I just don’t want to. But for me having lost everything through illness it’s a bit harder as I have to start all over again. Do I have time? Is turning 50 like this? A huge thoughtful event filled with fears and also filled with new knowledge. How do feel about turning 50? Is it true 50 is the new 40?