I'm 43 and feel the complete opposite. I am less coordinated and heavier than I used to be. I am learning advanced SQL for the first time and it feels like I am picking it up at a good speed, but still a bit slower than maybe if I were younger. I suspect this is more bias than mental degradation because I look at SQL and wonder why people would put such advanced logic into stored procedures which are limited by archaic conventions.

On the converse my primary programming skills have never been sharper. There is a caveat to this. I feel like I am an expert in what I do, which means I am confident in what I know and what I don't know. It also means there is a lot I have unlearned or intentionally avoided because such practices are anti-patterns or decrease productivity. Some of these things I deem "poor choices" are extremely common conventions which may indicate I am only a beginner from the perspective of a less practiced person who cannot live without such "poor choices".

I believe my programming skills are sharp because I am doing things outside of work that nobody else is doing. I have now reduced my OS GUI to a load time of around 165ms in Edge (130ms in Chrome). I saw a code package from Google on Github on the front page of HN either yesterday or the day before describing a means of file transfer cross-os. My personal JavaScript application has been doing that for years. Soon that personal JavaScript application will have a command terminal that executes in a web browser that works on both the local device and remote computers cross OS.

I once read about this in a book. I cannot remember if that was Blink, Outliers, or Good to Great. Performance follows practice, but the practice must be strenuous, such that you are continuously solving ever more challenging problems. Its the difference between a hobbyist whose skills will degrade over time, a professional whose skills are actively maintained but not advancing, and an expert whose skills continue to increase. As an example most senior developers I have met believe they are awesome because they are doing the same things they were doing 5 or more years ago, but now they are so much faster at it. That isn't awesome, its steady state.