Well, about 2 years ago I decided to learn russian.
Made my daily lessons (app counts a 687 day streak now)
And what shall I say, it paid off. It's not bad at all. Not gonna visit Russia it any time soon though :/

Same with Blender. Started a couple of months ago, was hard but it starts to look good.

However, it totally pays off to start learning something new, even if you do not make money with it directly