One Skill to Learn This Year

One skill I'd like to learn this year is...how to format my own books.  Don't get me wrong, I love my formatters. They put up with me despite my habit of finding "one more error." (There's always one more error, damn it). I'm not planning on throwing them over anytime soon; however,  I'd like to get to the point of being able to update the backmatter of my book without breaking all the pretties of the interior at a minimum. Then, level-up to Master of the Formatter Universe as time permits.