The celebration of St. Stephen's Day is a thoroughly civilized way to recover from Christmas.
Even before the big day, there are days of preparation and shopping and dashing that lead to exhaustion. By the time you've had the last bite of the Christmas pudding you're spent. There's not a drop of energy left and your poor old body tells you to lay low.
But when you've got to get up the next morning and go to work, hung over and riddled with indigestion, you won't be the least bit productive so what's the point? Hence, the St. Stephen's Day ritual of doing absolutely nothing.
All the shops in Ireland are closed so that the employees can rest. You'd not want to be out shopping anyway, not when you've shopped and already dropped. Besides, the crowds and noise would be too much after that last short whiskey you had when you'd already had enough.
Tomorrow is soon enough to meet the world again, refreshed and recharged. Go on, call in sick. Better yet, tell the boss it's a religious holiday and you've simply got to get to Mass and then there's a Rosary after and the Stations of the Cross and you'll be on your knees all day.
Well, some people will be on their knees all day but it's the porcelain god that they'll be worshipping.