Getting old isn't really a thrilling process for anyone, but I have yet to find a way to stop it , I myself and having issues with it.
But just because you age doesn't mean you can't still enjoy your life and have great sex. Im 48 my sex now is better than anything I had in my younger years lol
Are you in Therapy? If not please consider seeing a Therapist. he/she can help you process how your feeling and you can learn ways to still enjoy your life and that aging isn't the end of the good stuff.
I hope your feeling better and able to find some positive to focus on soon