Hissing isn't something to worry about, similar to a dog growling - it's a warning. It's a bad behavior, and I don't treat it as such. However, the idea SRMD94 had should be put into use if it comes to striking. In my collection, if a snake strikes at me or bites me while I'm handling, I don't react and continue to handle them until they calm down, and then put them back in the enclosure, because that way they might start to realize that biting gets them nowhere.