Actually losing weight, for real

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Hi there! 21 year old female here. I've been overweight since I was a child. Of course, there have been so many times where I told myself I was going to lose weight, eat healthier, and exercise. I occasionally had a week or two of motivation, and then it always died out.

Not this time, though. On August 25th, I told myself I needed to man the hell up, and I've been doing great since then.
I used to drink a liter of pepsi a day. Since I started my diet, I've only had a can of Diet Dr Pepper three times when there was nothing else to drink.
I've actually been exercising several times a week.
I've been eating less than 2,000 calories a day. (I aim for about 1850 but don't get too upset if it goes over a bit.)
I've already lost about 12 pounds!

I can feel this time is different. My mindset is different. In my previous times of trying to lose weight, I would often get overwhelmed by cravings. I'd break down and get a glass of pepsi, and pig out all night. Now when I get cravings, I make sure just to have a small bit of whatever I want, no pepsi under any circumstances, and make sure whatever I eat doesn't put me over my 2,000 calorie limit.

It's less about motivation, and more about discipline.

I've never lost this much weight before, and I've certainly never stuck to a diet for this long. Though I'm not so sure I'd call it a diet per se. I want this to remain for the rest of my life. I don't want to lose this.

I've told myself I can drink pepsi on holidays and my birthday. But I'm not so sure that's a good idea. I'm a little nervous that it would mess everything up. Pepsi is my weakness, lol.