Impossible Goal of Weight Loss (last 20 Pounds)

How do we plan for fails when our goal is weight loss? My goal is to lose my last 20 pounds in six months (well, five months now since I am just doing the work on this mid January). I am not sure what types of things to plan as fails or do we list things we want to do (this protocol or that movement goal or this urge plan) and know we will sometimes fail?