You can't know it all. No matter how smart you are, no matter how comprehensive your education, no matter how wide ranging your experience, there is simply no way to acquire all the wisdom you need to make your business thrive.Donald Trump - Learning - Business - Knowledge
In the programming world we hear this more and more often, frameworks have thousands of classes, functions and features, even the people behind those frameworks don't know other parts of the framework, what makes you think you can know it all
It's key to be comfortable with your own ignorance. Understand that you can't know it all and stop trying to or pretending that you do. Understand that other people are ignorant too, and help educate them when you can rather than resenting their shortfall. On the same track, don't resent someone who's trying to teach you something either, swallow your pride and better yourself for it.
My approach to this issue is to learn the language features as good as I can, then on the features of the frameworks I make a distinction on technologies that I'm interested in learning right now and learn them, and as many others that might be useful at some point, but the point is to be aware that such features exist and what they do; that way when you actually need them you can find them a lot faster because you know there is something to do just that and you avoid reinventing the wheel in many cases
services like del.icio.us can help you with this problem, if you see something cool that you might be interested in the future you can save a link and tag it with something like "future" and you can build a list of things to learn or that you can posibly use some time later
You can't put everything in your brain, so use the existing tools to do some of that work for you
Is just like in soccer, is always good to win, but if you can't win is good to tie, if you can't tie is good to lose for as little difference as possible