[commandlinefan]

> having not exercised those muscles so much fell out

I had the same experience - I learned enough to pass the tests and then forgot everything as soon as the semester ended. I picked it back up out of genuine interest years later and it was amazing how much I retained now that I was actually studying because I wanted to rather than because I had to. You might also be surprised how much you actually do remember, hidden just under the surface of your consciousness, if you do go back and try to remediate on your own.