I can honestly say I don't "struggle" to lose weight anymore, but the two things that were that hardest for me in the beginning was getting into the habit of actually going to gym everyday and not make excuses. Soon it became habit and actually now get agitated when I can't make it there.
In terms of nutrition, portion control was difficult but that came easily overtime, combined with my success at the gym, it made me that more motivated to eat better.
It just became part of my daily routine. I didn't have to think about it anymore. As soon as I got out of my last class, I drove straight to the gym instead of going to stuff my face like I used to. As the old myth goes, it takes 21 days to form a habit. Idk how to explain it in more specific terms but the whole process became "automated" without me being fully aware of it. Again though, this habit was reinforced as I saw the pounds dropping.
You might be interested in reading this thread:
http://weight-loss.fitness.com/topic/11956-why-hard.html