Ok so I have been eating healthier, I cut out junk food completely but their is one thing I have not been able to cut out. I drink a soda a day, I have to be awake all night and it helps me stay awake. I stay right under 1200 calories and exercising and have been losing weight steadily. Does drinking that 1 soda make a huge difference and throw off my diet or is drinking a soda a day while everything else is healthy ok?

If you've made a lot of other changes to your diet, I'd wait at least 30 days before taking on a big challenge. You will be able to tell if your program is working by how much you've lost in that time. If you're losing 1-2 lbs a week and having the pop, then it's all good. If not, you may want to consider some alternatives. Piling on too many new changes all at once is a recipe for disaster in my experience; it gets too overwhelming and I have a tendency to revert back to my last comfortable spot and give up all the changes because one thing was too hard. If I make a few little changes that are easy and one hard change at a time, then wait a bit until I feel comfortable with those changes, I don't get as overwhelmed and if I do give up I have some good habits to fall back to.

So long as you count it in your calories, it should be fine. I know lots of people avoid all liquid calories, but I do not. You have to do what works for you, and what you like.

I agree that as long as you are including in your calories and not treating it like it doesn't count, it's not too bad. If you are interested in cutting it out, I do think waiting until the healthy eating has become a habit will help. It is hard to make a lot of changes at once, so a little bit at a time is better. IMO, one soda a day is not a big deal, but this is coming from a diet soda addict!

You might find that you can do a fair bit to get ready to give up the soda before you actually give it up, too. Evening out your blood sugar, getting all the nutrition you need, getting good sleep and excercising to help get more quality sleep will all make it easier to stay awake and so easier to give up the stuff you need to stay awake.