You can't force people to live life the way you do, no matter who they are. It simply doesn't work that way. However, I totally understand where OP is coming from. I struggle with my own efforts with my weight loss journey -- I find myself giving into temptations quite a bit more than I should, although most of the time I do stay within my calorie limits. When I get home from school on the weekends, my parents (who are not dieting) usually have plans for big, unhealthy meals and I have to deal with it. They think it's okay to "reward" yourself on the weekends, and it's not. I don't want to "be good" Monday - Thursday just to sabotage myself on the weekends, it's really hard.
But you have to be your own boss and say no, which is something I struggle with. Just because Dad is having ice cream doesn't mean you have to have it, and if he gets offended, then you just have to say, "People don't lose weight by eating ice cream all the time -- I'll have to pass this time." Fathers are particularly frustrating when it comes to this because they think that what you're doing isn't necessary, but it is. And you have to remind yourself that.
Everything about this is hard, and you can't be perfect all the time. The people in your life can't be perfect all the time. You just have to find ways to make it work for you.

