Feeling Discouraged

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Now, I know I'm not overweight, but that doesn't mean that my weight and fitness goals are any less relevant. I started out at 123 with a goal to get to 113, but because I'm small already, it's been difficult to get there. I've been going to the gym daily- weight training 2 days a week and the rest cardio. I haven't put anything unhealthy into my body and I've been good about sticking to the stupid 1200 calorie daily limit, even though I feel like I'm starving most of the time. Just last week I had gotten down to 116.8 after 6 weeks of this. I was starting to feel like maybe I could just maintain that weight through the holidays and maybe enjoy some of the treats around me so I didn't feel like I was denying myself. So, I went out of town for the weekend to a lake house with friends. I was good and took my own foods- (fruits, veggies, protein) so I wouldn't completely fall off the wagon. I also got up and went for a long jog and a hike while I was there. I didn't drink anything but water, which is hard to do at a lake house with friends. I was there for 3 days- day 1 and 2 were good except a couple s'mores and eating lasagna for dinner (though I kept my portions in control). On the 3rd day, I decided to indulge a bit and ate the cinnamon roll for breakfast, and had the big Italian dinner and cupcake for dessert- it was just one day, right? When I got home on Monday, I weighed myself and was back up to 119- a 2.2 lb difference in 2 days. I hoped it was just a fluke, but I weighed myself again this morning and I'm still at 119. I feel so defeated! I worked so hard to get down to 116.8 and then I just ate like I used to for 1 day and I managed to gain over 2 lbs? How am I ever going to maintain weight loss when I do reach my goal? Am I always going to have to stay under 1200 calories and feel like I'm starving just to maintain my weight? Will I never be able to enjoy an Italian dinner and desert without gaining 2 lbs? What is going on? I'm incredibly discouraged and intend to hit the gym and eat healthy and start over again, but I can't help but worry how this is going to work in the long run when my body doesn't seem to want to establish any middle ground.