I can't retain information unless it's important. The only way you find out if something is important is to fly. Then you go back and look at the stuff you now know is important until eventually you don't need to look back at anything.
Funnily enough though I can recall numbers with no effort or learning on my part. I could quote you V speeds and performance graph data for anything I fly. Same with radio frequencies, I only need to dial them in once and I never forget them. The human brain is a fascinating thing. I may get one sometime.
Edit: Just cross posted with ST and I agree with him about being air minded. I never stop thinking about flying really, even lying on a beach somewhere I'll be watching the weather and trying to predict what it's going to do. Can't help it.