I really liked the suggestion about maxing your retirement funds first (401(k), roth, etc.), since cash will likely earn you more return, and it's easy to say "we can't pull out the money without paying huge penalties, I'm sorry dad/mom". The further you can remove the value from being "cash" (aka investing it), the easier it will be to think with your head.
That being said, I've heard worse reasons to pay off a mortgage... if you know you need to lock away money so you won't be tempted, buying an asset is better than going to the bar. :)
~ DaftShadow