I sure do know what mine is. My biggest challenge has got to be work. Hot fresh baked goods will always be my downfall- unfortunately I have easy access to them. I'm a baker and was raised by a baker. I work 40+ hours a week in a bakery, primarily cake decorating. There are always stray croissants, cookies & cupcakes floating around. The other downside is I'm on my feet all day, which makes it hard to work out after. Being a student also limits my work out time.
My family, although supportive, tends to help me backslide a bit. I come from an Italian family, which comes with big Italian dinners with plenty of breads, pastas, fatty meats and WINE! I never realized how calorie dense the wines I love are- which I've given up. It's become a hobby to find healthy, low calorie replacements for this stuff. I also enjoy making more of the already healthy Italian meals.
I envy thin people who don't have to think about being thin. /sigh/
What's YOUR biggest weight loss struggle?