I think too the more progress you make the more confidence you gain, then the more confidence you gain the more progress you make ! Take a break from it if you need to but keep chipping away at it if you are able. I remember something like dr Sarno saying if there were a scientific study on TMS it likely wouldnt work because only about 20% of people would get it sufficiently to make real progress (Sarno was such a master at teachign it though it was much much higher with him), between the depths and comnplexities of the unconscious mind, the complex role of fear, the skill set of the therapist or MD treating, and the difficulty in reframing the meaning of the symptoms by the patient; it aint easy....
One thing I do when I am in your mental boat is look at the Schubiner study on fibromyalgia as I have those symptoms like you, and all of the other studies and most of the patients are often back pain or at least not so bad as us fibro symptom folks. I also think that with fibro symptoms you have one of the most severe forms of TMS, so even though with back pain 20% need therapy I think it is much higher with fibro; for me at least this has been the case. I dont know how I would have done without therapy by a TMS specialist but likely I may have not seen a large amount of progress and eventually gotten burned out with all the effort and not enough results. Here is the schubiner study....
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2955480/