Humble pie a la mode

I'm loving the new job (well, one of them) and the people with whom I work are committed and focused.  It's an adventure going into Boston every day for the first time in fourteen years, and it's quite nice to watch the savings account grow just a little once every two weeks.  The learning curve, however, has become a lesson in humility.  My aged brain, while amazing in its ability to remember many many new names, is showing some wear and tear when I try to figure out the accounting system.  Or to put it another way, the people in the Accounts Payable Department are wondering if I am on drugs.  There's this spreadsheet, you see, with too many columns and codes and numbers and stuff.  There was a one hour conference call with the director of AP who just couldn't take it any more and had to try to pound it into my head herself.  And then there was the royal mess I made of it, which had me feeling inadequate as I pondered it at three o'clock this morning.
If I were my own best friend (which I usually don't manage to be) I would tell myself that I've only been there six weeks, that I should cut myself some slack, that it will come.  In my more enlightened moments I realize that while people are trying to learn to walk with one leg, and others are wondering where their next meal will come from, my feelings of inadequacy are rather small potatoes.  Still, one worries:  "Is it because I'm getting old and my brain can't hold any more?"  There might be something in that.  Or it could be lack of sleep.  I'll get it.  I'll make myself get it.  But it bothers me that I make mistakes that others can see.  Wouldn't you think after six decades I would have figured out how ridiculous THAT is?