Ask HN: What should I learn next?

For the better part of the last 2 years I've been freelancing part-time as a Wordpress developer, focused mainly on building custom themes and modifying existing plugins. Naturally, this meant PHP was the thing to learn, since I was already familiar with HTML/CSS, and 99% of the time, a bit of jQuery on the side was just enough to get the job done. However, after taking a break for a couple of months in order to focus solely on school, I've realised something pretty scary: I actually suck at programming. What I mean by this, is not that I can't code ( I've pretty much learned programming by myself and am passionate about it ), but the fact that this entire time I've been half-assing it, and now I find myself in a place where I'm not really good at anything. I mean, I know a little bit of C that I picked up in school ( although no OOP ), enough PHP in order to be able to write simple functions that hook into Wordpress, a little bit of Ruby I picked up