Change is situational. Transition, on the other hand, is psychological. It is not those events, but rather the inner reorientation or self-redefinition that you have to go through in order to incorporate any of those changes into your life. Without a transition, a change is just a rearrangement of the furniture. Unless transition happens, the change won't work, because it doesn't 'take'.
William BridgesNothing so undermines organizational change as the failure to think through the losses people face.
William BridgesWe resist transition not because we can't accept the change, but because we can't accept letting go of that piece of ourselves that we have to give up when and because the situation has changed.
William Bridges