Apparently the tradition of New Year's resolutions goes all the way back to *Roman times:

It’s said that Julius Caesar started the tradition of making resolutions on January 1st as a way to honor the Roman mythical god Janus, whose two faces allowed him to look back into the past year and forward to the new year. 

*(Updated Jan. 2, from the original article which mentions that resolutions go back to Babylonian times, but doesn't provide the proof. Thanks trusty Dish readers! – Z.P.)