Join Date: May 2007
Location: Fairbanks, Alaska
It sometimes helps to think of it as a forward/back motion rather than up/down. At some point, you do not want to be posting from your feet/stirrups, but from your thigh. As said, you should be able to get to the point where you can do it without stirrups, but until you get the patter/motion of it down, it may be easier just to use your stirrups to help you.
I don't think you put your foot in your mouth about not posting on trail - it is just a neat trick to be able to go long distances at the trot on trail without feeling like you are on a jack hammer. Yes, WP horses have a very sittable trot/jog, but when you get a horse out on trail, and they get their rhythm down, the jog is much quicker, and more of a pain to sit. :)