The sun was out and I loved my life. The sun is down, and suddenly I'm reminded it doesn't matter

At this point what is even the point. I am happy. I am in a good place in my life. I have all the resources and capabilities. If you knew me you would never even begin to think I had anything lacking. Why, why, why, why then. Why is one bout of midnight nostalgia enough to drag me right back into these pits of ideation. I've been free for years. Even after my divorce it wasn't this bad so why now. Why now? What's the point if I'm this unreliable to myself. What's the point of being able to remember if I can't go back in time?