When you're trying to motivate yourself, appreciate the fact that you're even thinking about making a change. And as you move forward, allow yourself to be good enough. Perfectionism can undo what you're trying to achieve. Look at the angst people have when they cut a workout a little short. Do they really think a few minutes less, one day, is going to make that much of a difference? Worse still is the "what-the-hell effect"—you eat one bad thing, then just give up.
Sabotage can also come from those around you, even your loved ones. (That may sound irrational, but in my experience, many spouses go through this.) It's threatening to people when you start making positive changes. If you're about to go on a diet, you might want to assure your husband, "This isn't because I want to be hotter and am going to leave you. I'm worried that if I don't lose weight, there will be health consequences." Use honest, loving, clear communication. You'll need all the support you can get.