Do you ever have trouble learning outside of work? I certainly do. In college, during the summers, I felt like I had tons of time and concentration to dedicate to personal projects and ideas. Now, when I try to pick up a technical book outside of work, my brain stalls. Have the time, when I try to pick up a technical book at work my brain stalls. Here's my theory. Your brain is like this:
And the water is all of the topics you're expected to keep
track of and have ready on a moments notice when your boss or coworker asks you about them. There is no way you can actually keep track of all of these topics, some of them spill off and you need a refresher before you can talk about the intelligently.
Then, if you're trying to learn, you're brain does this.