Motivation takes work and motivation is what it takes to stick with a good fitness plan. Staying motivated is a challenge that you can meet but you need creative ways to do so. I like the article that I am linking to because the author recognizes that staying motivated takes work. I hope that his tips help you. I especially like his tips to "step on the scales regularly" and to 'set realistic goals". You cannot improve if you do not measure.
http://www.freep.com/article/20120104/FEATURES08/201040316/Successful-weight-loss-needs-right-motivation