When you've dealt with an eating disorder, you often encounter these situations as you try to recover:
You skip a meal.
You purge a meal.
You eat something "scary" but exercise to make up for it.
You get an invitation out to eat, but are too nervous to go.
You go out to eat, but you eat only "safe" food.
You go out to eat and you purge your food (to be safe).
And so on.
When these behaviors add up or take place over time, they can get pretty frustrating. It feels like you'll never get better, like you have to keep doing these sorts of things or you'll go crazy/get fat/be unworthy...
But I think the thing that changes... is when they have been in recovery for awhile, and begin to see the patterns--they begin to see that at times, yes, they have messed up. But many of those times, that doesn't mean a complete return to an eating disordered life. It just means something got a little too crazy and out of hand before you could step in and think through it, and that you need to learn a way to keep it from happening again.
Another thing that changes is your perception of recovery changes. You may begin to see yourself in recovery ever since the first day you began to doubt that you wanted to live the rest of your life sick. An no matter how sick you were after that, it's all a big lesson to learn from.
Because you have to choice to treat yourself better even when you make the mistake.
You just need to have the courage.