You can't teach a pig to sing. It's a waste of time and it annoys the pig. - source? unknown.
I was recently reminded of this old saying. A project manager's primary responsibility is not to provide singing lessons, but to evaluate if singing lessons were required, will have affect and will provide benefit....but sometimes you don't realize this prior to annoying the pig. Oink, oink little pig!
(image via http://www.sacatomato.com/2007/03/oink_hug_a_pig_for_national_pi.html)