This tradition goes back further than you might think. The ancient Babylonians are the first people to hold recorded celebrations for the new year (which for them was in March, to mark spring crops being planted), reports History.com. These celebrations began about 4,000 years ago and consisted of promises to the gods to repay debts and vows of loyalty to the king.
According to the Economist, ancient Egyptians also had New Year’s-type rituals, in which they made sacrifices to Hapi, god of the Nile, to mark the annual flooding in July. And beginning around 46 B.C., after Julius Caesar changed the calendar to make January 1 the beginning of the year, ancient Romans honored the god Janus on this date. In these rituals, citizens also made sacrifices, and promised to behave in the year ahead.
As time went on, the tradition of New Year’s resolutions changed, but never really disappeared. As Christianity spread, January 1 became a day of reflection and repentance for past sins, and people made promises to do better in the year ahead. Slate notes that in medieval courts, knights may have made post-Christmas vows of chivalry by placing their hands on a roast peacock, called the “peacock vow.” (The sourcing isn't super reliable on this, but it sounds cool.)
The 1600s marks the first known use of the phrase “resolutions” in connection with the New Year. Merriam-Webster says Scottish writer Anne Halkett wrote a diary entry in 1671 that she titled “Resolutions” and filled with pledges, many inspired by lines in the Bible (including, “I will not offend any more”). In 1740 John Wesley, founder of Methodism, created a holiday called the Covenant Renewal Service, which included making promises for the year ahead. It’s still observed in some Protestant denominations today.
The phrase “New Year’s Resolutions” first appeared in a Boston newspaper in 1813. By that time, New Year’s resolutions were more secular than religious. According to the BBC’s History Extra contributors Sam Willis and James Daybell, on January 1, Victorians traditionally looked back on their mistakes and made promises to “[avoid] habits and customs that have been injurious.” And just like today, many people broke their resolutions: An 1883 editorial in the Worcester Journal notes, “it unfortunately happens that New Year's Day resolutions are often of the most transitory kind, and they pass away almost with the mists of the morning on which they are formed.”
So if you break your resolutions by January 10, remember that people have been doing exactly the same thing for hundreds, if not thousands, of years.