Often our New Year’s resolutions are lighthearted, and usually, the flesh being weak, they are fleeting. Before Valentine’s Day or maybe even before Epiphany, we have slipped back into our old ways. But these lighthearted resolutions reflect a deeper, more serious impulse.

At the time of the American founding, celebrations of Christmas in America varied widely, from Puritans and Quakers who shunned or ignored it, to other Protestants and Catholics who honored it in their own Christian ways, to those who spent the day in “riot and dissipation,” like an ancient Roman...