Language. I've learnt several physical stuffs (e.g. bodybuilding, music), several emotional stuffs (e.g. meditating, music) and other intellectual skills (e.g.

Language. I've learnt several physical stuffs (e.g. bodybuilding, music), several emotional stuffs (e.g. meditating, music) and other intellectual skills (e.g. game theory, the humanities and programming of course...) and if I had to choose one to recommend to the HN community, it's language. Unfortunately, it's high reward [0] also comes with high effort. Even with the best resources, it will take time and patience. But you can start at anytime of your life and at anywhere. [0]: https://www.youtube.com/watch?v=MMmOLN5zBLY https://www.youtube.com/watch?v=MMmOLN5zBLY