Go learn something. Go write something. You'll feel better soon.

The longer you stay in this business, the more tools you'll learn, and the more tools you learn, the better-equipped you'll be to handle the particular requirements for which a particular language is designed and well-suited.

There will never be a point where you can kick back, toss your knapsack on the table and say, “Well, I've arrived!” This industry in particular is always main-lining growth hormones. It reinvents itself literally every few years. The present cycle, of Windows® dominance in a now-major market segment, is “only” about 20 years old, and already well on its way out. “The web,” well-entrenched though it may appear to be, is barely out of its diapers yet! The next cycle is clearly foreshadowed by iPhone® and other forms of handheld personal electronics. It never stops, and it never will.

Don't be alarmed by what I'm saying; don't let it stress you out. This business has always been this way ... it was “this way,” so I'm told, in the 1940's and 1950's. I think that's part of what makes it so engaging and interesting. “Don't Panic!™”

You must constantly acquire new skills and develop your proficiency with existing ones, just to stay in the game at all. You're also going to have to specialize; it is physically impossible to know it all, or even, some might say, to know very much.

So for example... yes, you need to acquire enough of a cursory familiarity with Ruby® (and Rails™) to be able to “land four-paws-down” if a project presents itself in that language, or to provide knowledgeable advice as to whether it should be used. But you have to add that awareness to your tool-chest; it will never replace what's there. You don't have to become (say...) a Ruby über-geek, unless you want to. You just need to have seen it before, and to know what it might be good for, and to be cursorily aware of where its warts are, too.

In the long run, people are not hired to be walking encyclopedias. (That's what encyclopedias are for.) They are hired for their expertise and their experience, their reliability, integrity and skill. Tim O'Reilly is always going to be publishing a new book and he's always going to want you to buy it, but you don't have to pack his entire library between your ears and you're never going to be “unemployable.” If you're any good at all, you're always gonna have as much work as you care to do, no matter what you do.