Personally, I focus on small goals and surround myself with a supportive community for encouragement. Keeping a positive mindset and understanding that progress takes time helps me stay committed to the plan.
You know what else doesn't help? When your teenager brings home the large size Dean's French Onion Dip (in all caps) and a few bags of kettle chips. And they decide they don't like it. That's like putting crack in front of an addict.
I usually get derailed by family stuff. My husband doesn't like "healthy" food, like fruits/veggies, so I tend not to cook a lot of them.
For exercise, I find that sneaking in just a few minutes of stretches, doing a little extra house or yard work, etc keeps me moving. I've considered joining a gym, since I can get it free through my insurance supplement, but I figure there's no point. If I don't use the treadmill in my spare bedroom, it's unlikely I'm going to make use of a gym membership.
Because much of my weight issues are health related (thyroid, insulin resistance, etc) I find myself having a hard time staying motivated to keep up with a specific plan.
To stay on top of an action plan around weight, I am able to manage my eating, but think I will always have to do an exercise class, or just won't exercise in a consistent way. I haven't found any personal training that stuck, so am looking into Pilates.