I have faced this problem in childbirth classes as well as talking about
breastfeeding. There seem to be two philosophies; one says that if
we talk about the P word (as one chldbrith educator called it) then
we somehow make it happen. The other side says that if we don't talk
about it women think they have failed if they experience it.
  I think a lot of this has to do with our (mostly western, even
American) attitudes about pain. WE have the feeling that it is something
to be avoided at all costs and that life should be pain free. It's not.
Some things  in life hurt. In labor, pain is an indication of hard, productive
work. IN the case of breastfeeding it may be the same thing or it may be
an inidcation that something is wrong.
  IN either case, I come down on the side of letting women know that
there is pain and sometimes that's ok. I also let them know that the
experience of pain is VERY subjective and that no one can tell anyone
else how much pain is too much for them to bear. ANother thing is
that pain is worse when one is tired (my experience is that people ask
for pain meds in labor when they have been in labor for a long time and
they are exhausted) and when they don't have a sense when (or even that
the pain will end. If you know that it is time limited, you can usually
live with a lot more than if you think it's going to go on "forever"
  The International Journal of Childbirth Education put out by
ICEA had an issue dedicated to pain a couple of years ago. I had an
article in there as well as a number of other interesting ones looking
at how to think about and how to teach about pain.  The issue is
vol 10 no 4 (NOv-Dec. 1995)
  Sorry for rambling so, this is something I've spent some time thinking
about.
  Naomi Bar-Yam PhD