I'm a great believer that if you are making a big change in your life, like losing a lot of weight, giving up smoking etc that it has to be because you want to, at least if you are doing it for you you'll put in 100%. I reckon we are definitely setting ourselves us for success because we choose to lose weight for us, so many people fail because they are doing it for someone else.
Don't beat yourself up to much, it is totally natural to feel miserable when you make a lifestyle change, it's going to take time to get use to. I think it was 21 days to make something a habit . . . . give yourself time.
The important thing is to concentrate on what you are doing right, the positives of the situation. Every change you make, no matter how small, is a change that brings you closer to your goal.
You can do it, we are all right behind you,