Learn TLA+
I'm a bit skeptical of TLA - while I'm not so full of myself that I believe there's nothing I could learn that would make me a better programmer, TLA has always seemed... awfully dubious.  In fairness, I haven't devoted more than a few minutes scanning over it, but I've also never seen or heard of anybody else using it (but maybe I don't travel in the right circles?), much less getting any benefit from it.  The examples always seem awfully contrived and prone to exactly the same sorts of problems that code itself has.  The promise, if I understand it correctly, is to have a way to nail down the design before you start coding so that you don't have a whole class of surprises (bugs), but this extra non-debuggable step actually seems like it would be worse.