Frusterations with the Post Office

I'm mailing a couple of books to Tony, so he doesn't have to buy them to read them. Why have a tiny libary if you can't share it? So I pack them in a priority mail box that I had lying in my basement from something that I bought off of Ebay. At the mail counter the mail lady says that I can't mail them via media mail in a priority box. It just seems so damn stupid that I can't recycle this box to get more use out of it. I'll have to find a different box now that'll work and repack. This is one of the things that drove me to near madness that I used to be able to brush off.