21 day window of Mastery

Ok, we've heard that it takes 21 days to form a habit. Also heard that if approached with a lot of enthusiasm and dedication of 11 hours a day for 21 straight days, one can master just about anything. In a typical work year, one can find at least 210 workdays. So this leaves us 10 opportunities to pick our 21 day window of mastery! What do you want to master? A musical Instrument, a form of art?, a subject you considered yourself weak at? A self-development skill? Golf? You name it! And go get it.. How'z that for a New Year's Resolution?