My trainer has me walk with weights all the time. Usually, I'm doing something with those weights - lateral raises, bicep curls, shoulder presses, triceps, etc. On occasion, he just adds extra weight and has me walk with him. On Monday, I got to walk a lap (0.1 mile) with 40lbs in hand. Do you know how heavy that felt? And to think three years ago I weighed 70lbs more?
When you need a little bit of motivation, grab a weight that equals what you have lost and walk for a bit as a reminder of where you once were. It'll get your butt in gear again, guaranteed.