Strongly agree with "programming", but strongly disagree with "learning an instrument". I wasted lots of time on that. The costs are high, and all the benefits are either dubious or can be more cheaply obtained through other means.
I, on the other hand love my cello. I also happen to enjoy practice itself. This helps a lot.
This is the question asked by John Cook on Twitter. He lists responses from different people:
Mine are: quantum mechanics, Python, cooking, the language of philosophy.
What learning curve do you wish you'd climbed sooner? Give reasons and stories if you feel like it. Do you think other people should climb the same curves?