After Christmas everyone says, "Did you have a good Christmas? What'd you get for Christmas?" etc.
But St. Patrick's Day is an island among days. It's there, you're wearing green, then it's gone. No follow up. People at work aren't commenting on what a great St. Patrick's Day it was, etc. At least in my experience.
I suppose there are plenty of hangovers. But those aren't usually a happy thing.