A year and a half ago I wrote an article about oomph- the mysterious power behind all our endevors. I just reread it and discovered there were a few references to walking, and how my early attempts at long distance walks failed through lack of oomph. I think it's worth another look so here is the link:
http://www.roberttwigger.com/journal/2011/1/20/the-power-of-oomph.html