Every project has a desired outcome and every change has its own resistance. Successful change management involves changing the way people think. Resistance may come from many levels: co-workers, the management and many others involved. Remarkably, it seems like every person deals with change the same way.
I found a really clear model on the internet (right here), explaining the five phases of change people go through and how to cope with those phases as a project manager. The phases are: unawareness, awareness, understanding, believing and acting.