Last year, I made 7 goals as my New Year's resolution. You can find the results here, here, here, here, here, here, and here (and the conjunction here). That is only a 29% success rate. I attribute this low rate more to unanticipated value shift (mostly caused by the birth of my son) than to picking overly difficult goals. On the bright side, my calibration still appears to be pretty good at 50/50, 62/60, 75/70, 81/80, 95/90, and 96/100.