From my point of view, we get a new project that I think will take 6 weeks because of X, Y Z. Management thinks it should take 2 days, so they say go ahead anyway. The project takes 8 weeks to finish most of the features and doing this effort forced us to drop every other thing we were already maintaining and working on. Everything is late, the targets set for the year miss as we spent 2 months on this other project and nobody is happy.