bag of hammers

Someone who looks like they're carrying the weight of the world on their shoulders, is very upset, or having a really bad day. A bag of hammers is heavy and cumbersome. Thus, the "weight of the world" on your shoulders.

You seem to have had a bad day. You look like a bag of hammers!!

that's a you problem

That's a you problem. (In other words, it's not my problem. Deal with it.)

Person 1: I don't know how I'm going to get that money back to you before Friday."
Person 2: That's a you problem. I want it before Friday.