I remember when I first started losing weight. I was in upwards of over 330lbs., so when I began losing weight, it came off pretty rapidly. This lasted for a good three weeks to a month before my 10lb. weeks dropped to nearly half that. At that point I was forced to make a decision. Would I continue on even though I wasn't dropping the weight as fast? Or would I choose to quit since it was going so much slower for me than what I wanted. I think it's obvious I chose to keep going.
Nobody can expect to lose an enormous amount of weight every week you weigh in. Your body will naturally fight against this as it's trying to "normalize" itself and get used to the new healthy lifestyle your trying to live. The best way to prepare for this slowdown is to know about it. More often than not when this slow down occurs, many people start to wonder if what they are doing is right. They start second guessing their diets, and start incorporating new and sometimes unnecessary things that do nothing but slow them down more. If you know about this process, you can plan to make small but healthy changes to your weight loss system to continue on the right path.
Remember that a healthy amount of weight loss is no more than 2-3 lbs. a week. Any more than that and you will be eating into your muscle AND fat, instead of just fat. You will need your muscle to continue aiding in the metabolic changes in your body promoting weight loss.
If you keep in mind that weight loss is a marathon process you will be much better prepared to deal with the slight changes that may occur in your weight loss journey. Good Luck!