Most of the time unhappiness is about perception of the world, not the world itself. There doesn't have to be an aging crisis for anyone. With age comes grace, wisdom, the ability to laugh and invaluable memories. Nothing wrong with that.
If you're dealing with anxiety and depression and think it's hindering you from living a full life, talk to someone. If that person isn't helping, talk to someone else. It's normal for your age to experience wildly shifting moods and depression. It's not normal if it's cause by a neurochemical imbalance.
When perception shifts, the world can look a lot friendlier. Go outside, look at the sky. Drive to the ocean. And talk to a qualified professional. Good luck.
