I had that exact same problem when I was mentoring a new DBA. I was explaining transactions, how the transaction log worked and why the ACID properties were important. And could I remember what the 'I' in ACID was an abbreviation for...
I recommend mentoring to everyone. If you can't explain the basics simply to someone new to the field, then there is a good chance that you don't fully understand it yourself.
Now, I have to go look up the exact definition of the Third Normal Form before someone hits me with it.