I really need to get out the "you screwed me over without meaning to" in a more politically correct manner...
There is SO much work and if there wasn't an opportunity to hire someone else, I wouldn't complain... I would just do the best I could to help.
But, now? Knowing that they're hiring someone to take the title of the job I used to have (and want) and they want me to do the things I used to do about fifteen years ago? (which I don't want).
Sigh -- talk about being unmotivated.