
When you have to exercise and you're not used to it, say no to sugar when you've lived on it, say no to carbs and yes to veggies when you've lived on crap food for years, when you have to plan and you never have, when you have to be accountable and you never have, and thousands of other new things. . .you can become overwhelmed very quickly.
First thing I did was take an HONEST look at what I was really eating, calorie wise, for a week. I used to think "I don't eat that much, why am I so fat???" because I only ate 2 meals and one snack every day. Well, when that consists of over 5000 calories daily, no WONDER I was so fat!!! So then I picked the major deal breaker, soda, and completely cut it from my life.
It took a long time for it to become a habit to reach for water instead of soda, but when it got to be easier, I picked another thing to change. Veggies instead of pasta/potatoes/rice. When that got to be easier, I started moving more. Walking for now, but hopefully soon will graduate into something more strenuous. And I will continue to change things on a small scale so that I'll be able to live with it forever.
What use is it to change your lifestyle if you can't sustain the changes and it only makes you feel guilty?
Hope you can find your key.