I've come up with new word for your dictionaries.
Irrationalisation: Noun. 1) The mental process of finding excuses or reasons to still do things that you know you shouldn't really be doing. 2) Rationalising using broken logic.
- Related forms: irrationalise (verb)
This is something I think all World of Warcraft players have to do once they reach the level cap. I know I spent the entirety of last night doing it...