Roy Kiessling, a prolific EMDR trainer and innovator, has come up with a great idea for EMDR. Instead of coming up with a different negative and positive cognition on the fly, right before processing, find the general negative belief or beliefs that underlie the client's life during the first stages of therapy. During the history-taking phase and the preparation phase, when there's no hurry, and you can delve deeply into the clients' perspectives and overarching schemas, you can find a sentence that brings tears to their eyes and sense of being truly understood to their hearts. When it's time to do some processing, you can say, "does 'I'll never get it right" (that core belief) still fit this situation?" Then go to the already configured positive belief and your off and running.
This weekend, during the training, every participant experienced a profound shift when they cleared the core belief/schema during processing. For some of us, the knowledge of the belief was sufficient to make some changes.
If you're an EMDR professional, you may want to contact Roy and sign up for this training. He's also giving Basic EMDR trainings, that include this focus. If you don't do EMDR, you may want to organize a training in your town. You can find out more about Roy at http://www.emdrconsulting.com/