It depends on how they are difficult. As a personal trainer, I've had some difficult clients. Some were challenging because they lacked confidance in themselves. Some have had emotional, behavioral or focus issues. Some have been just downright rude. After 34 years in the industry, I let the rude ones go and the ones that I cannot help, for whatever reason, I refer them to the appropriate place/person. Most of the time, my clients are a joy to work with!