Case in point was myself when I was learning Javascript. Sure, I could get the JS to do what I wanted, but it was clunky, used a lot of memory and was slow. Fast forward a few years and I've gone back and read Crockford's books several times, and with more studying, I've gotten much better at writing JS. I now try and make my JS as lean and as fast as possible. It's a totally different approach then when I started.
The problem is thinking once you know how to do something, you're done. Like a friend once told me, "You don't learn to be a programmer, you learn to be a student of the language you choose."