Successful at losing weight, but now all I think about is exercise: when is a good thing too much?

I'd like to know if others have experienced this same thing with weight loss and their mental well-being:

I have lost 8 pounds over the last 3 months, so my weight-loss has been successful but slow (which, I guess is the healthy way to lose weight). I am now in the "overweight" category by just a few pounds, so am very proud of myself! I used to be fairly athletic in my younger days, and am finally feeling like I can exercise without being sore for weeks, I can say "no" to sweets, and find food filling, satisfying and can enjoy a snack in the afternoon without guilt. I am much more energetic, feel stronger...life is great! I've got 10-15 more pounds to lose to be at an "ideal" weight, and about 3 more pounds to lose to be back in the "normal weight" category. Yeah!

So, since I've finally got this diet and exercise thing headed in the right direction, I'm noticing that I am paying attention to my food consumption and exercise every day...so much that when I am with my friends, I'm thinking about when I can get to the gym next, and I have nothing else to talk about with people! It's almost like my entire mission is to lose this weight and get healthy (ie, lower my cholesterol, for one!), and that this mission has consumed my normal, every-day ability to talk about other topics. I almost feel like I am extremely boring if the conversation does not revolve around food or exercise, and I don't want to be selfish and talk about myself; I know there are many important events going on in the world, and I love hearing about my friend's lives, etc.

Is this "preoccupation" a normal part of the weight-loss cycle? I'm not afraid of becoming obsessive or losing too much weight, but I'm not sure how to focus continuing my losing weight while having time and mental-energy for the rest of life.

I'm hoping that this is a normal part of the cycle, and that I'll be back to my regular "conversational" and "non-preoccupied" self after I've reached my goal, and can just maintain my weight without so much effort and mental stamina. Has this happened to anyone else? I've struggled to lose weight; it's been really difficult to re-learn how to eat healthfully and get to the gym most days of the week, so I want to keep this momentum going.

Thanks!