The short answer is I'd learn to focus on people and communication. Tech is really important, but so is being able to work as a team and achieve company goals (which might not be served by the shiniest new tech).
A lot more here: https://letterstoanewdeveloper.com/
Sure, learning Java, or C#, or Python is nice. But what really makes an effective worker to me is someone who has strategies for tackling problems, and I believe that the highest abstraction of that is self-discipline.
When you are tasked with a problem in the real word, whether it be enterprise, start-up, or side project, you will need to look at the problem wholly. You will need strategies for laying a path that you, and you alone can follow.
There's so much to writing software, but every developer wants to type. Do you have a good method for discovery? Understanding unfamiliar project landscapes, or code flows? Are you practicing reading code? If a manager gave you a project in a project you've never seen before, how do you know where to start?
Do you have a strategy for note taking? For flow charting as you discover? For documenting minutiae as you come across it during development? If you do, are you consistent? You need to be diligent and habitual in your process. If you present problems in a consistent manner to your manager, you will developer an easy means of communication, allowing you to solve things faster, and get what you need faster.
Are you consistent in your coding style? Are you implementing according to the problem, or according to whatever new tool you most recently discovered. That's engineering discipline.
I didn't really get there until I was in my late 20s, but it took some seriously trivial changes in my life to get started on that road. Like, I started making my bed every morning. Reading before bed, making a small breakfast, and coffee before work. Walking twice a day. Gym at lunch.
Having a schedule, being habitual, helps you get in the mind set of optimization. Optimizing your own processes will lead you to consistency, and sharpening your consistency will force you to be disciplined!
If you want to focus on your health, then you might want to set up an exercise routine and good diet. This is useful for offsetting sitting at a desk.
If you are talking about tech, then maybe you can learn about something that interested you but that wasn't taught in college or do a deeper dive. Experiment with Pi, or create an Android app, etc.
On a personal level you can start a new hobby. Maybe start a garden, make your own soap, learn an instrument, etc.