So far, my worst rejections are the terse ones. "Your work is not suitable for our publication" or a hundred variations thereon. Better are the ones who nice: "This is an interesting piece, but we don't have a place for it, best of luck, etc etc." I was lucky enough to get an acceptance after only a few rejections, so I have a bit of flotsam to cling to in the wide sea of rejection.
Keep paddlin'
Keep paddlin'