I found that setting small goals has helped me. I'll set myself aside so many calories for breakfast, lunch, and then dinner. You gotta keep that number in mind when picking out what you want to eat instead of just eating and then figuring up how many calories you just consumed. Know before hand. As for cardio, I hate exercising so I make myself walk on the treadmill 10 min at a time several times a day. I tell myself I have to walk a min of 30 min a day.
Have confindence in yourself and stick to it. Good luck and have fun at the lake.