What's something you signed up for that cost more than you expected — not just money?

I'm thinking about the choices we make and the price tags nobody talks about. The article about AI adoption hitting the dollar-sign shock got me thinking: what's the thing you took on — a job, a relationship, a move — that ended up costing you in ways you didn't see coming? I've got a few of my own, but I'm curious what others have found.