Hi Sue... my preface here is to say I don't in any way suggest you have low self esteem... I have read way too many of your posts to think that!!! I think the following is interesting because you could generalize beyond self esteem to what one 'knows' or thinks or is even afraid might be true about their body. I think you could substitute pain for self esteem.
This is from a study that was published in June 09 in the journal Psychological Science and was led by Joanne Wood:

Dr Wood suggests that positive self-statements cause negative moods in people with low self-esteem because they conflict with those people’s views of themselves. When positive self-statements strongly conflict with self-perception, she argues, there is not mere resistance but a reinforcing of self-perception. People who view themselves as unlovable find saying that they are so unbelievable that it strengthens their own negative view rather than reversing it. Given that many readers of self-help books that encourage positive self-statements are likely to suffer from low self-esteem, they may be worse than useless.

I just thought that was interesting (and then it bummed me out ).
cc