Right, definitely not fail-safe and you probably need some measure of luck to start out with the right dispositions (though my starting out a RationalWiki-esque leftist and ending up a pseudo-reactionary is evidence that at least sometimes it's not super important), but the most obvious alternative is just getting stuck being boring doing boring things.
That said, I generally have had ridiculous amounts of sheer luck—no, general positive outlook and so on really does not explain it, trust me—and so I generally don't know what's safe to recommend. Vladimir_M's told a story about how listening to the advice of someone high status ended up hurting him a lot, and what he did sounds sorta similar to what I'm recommending, so major disclaimers apply.
So, transferable skills: skills that, upon improvement, increase your ability in other areas (and also improve other, higher-level skills).
A basic example would be reading/writing. Knowing how to read and write allows one to access a huge amount of other skills and resources which are otherwise unavailable. A less obvious example would be clear speech (enunciation). Ability to speak clearly improves one's prospects in a lot of different areas (e.g. professional advancement, dating, etc.).
I'm looking for additional examples. Which skills did you find to be most transferable? Did you become proficient in X, and then found this helped you in many other areas of your life? Please share.
(I tried to find whether this was discussed before, and failed; if it was, I would appreciate the link.)