One of the most common mistakes made by childbirth educators is the tendency to understate the pain. Many couples gain a false confidence as they draw near to labor only to find they were poorly prepared for the intensity of the pain. I certainly felt that way in my first labor.
"Pain is inevitable. Suffering is optional." -M. Kathleen Casey
One should never understate pain, rather plan, prepare, and work with it. If you want to achieve an unmedicated birth you must exercise regularly, practice relaxation and breathing techniques, define roles of your birth attendants, and create a strategy with your coach. If you're not willing to commit to regular practice, you'll want to consider the epidural as an alternative coping tool.