First off, you aren't failing. You are struggling. It is hard, but let me tell you, it is sooo worth it! We all have our "slip up" days but you just have to take it one day at a time. The thing that's hard for all of us to realize is that regardless of who we are hanging out with ultimately we are the ones responsible for our success.
If you are having a hard time getting enough protein I know for me, those days are usually because of lack of planning. In fact, tonight I'm planning my meals and snacks for tomorrow (I do it only for the night before so I don't get overwhelmed) and then packing it. As far as soda goes, I had a super hard time giving it up but I just quit cold turkey. It's not worth it.
The one thing that has kept me totally motivated is hearing about people eroding their bands and having to get them removed from over eating and things like that. You can do it, you just need to realize you are worth this and you have an amazing tool that will help you succeed if you allow it to!! Seriously, see if your Dr's office has a support group, or come on here for support. Get back on track and become the best you you can become!! We're all rooting for you!!