One of the best things I ever did was quit a job I absolutely hated.
I too sometimes struggle with multiple orders because it can get monotonous but if you keep several projects going at once you can start on one while waiting for another to dry. That's the only way I've found it to be profitable especially if you look at how much you make in leatherwork per hour. Having multiple items in progress helps me to be able to have some variety.
Just yesterday I was working on three identical custom ordered pancake knife sheaths. By the time I finished tooling the second one, which wasn't very intricate, I was bored with it and the third one I had to talk myself into doing. I love it when someone comes to me with something I've never done before. Even though those tend to take longer because I have to start with nothing more than an idea or picture but that's part of the art.