I'm 24 and will be two years out in October. Like you I've been overweight my whole life. I'd lost weight on my own a few times - 50 to 60 pounds through eating very little and excercising like a madmad only to gain it all back and then some when I got discouraged. Then my doctor and I decided to have this sugery (I have the Realize Band) to use as a tool to help lose the weight and keep it off. I was just as worried as you were when I first started: what will happen if I fail? What will happen if I succeed? For my first six months I lost probably 30 pounds. It was really hard because my fill wasn't tight enough and I could eat just like I had before. I started to get scared that I was one of those people that this band just wouldnt work for. Then in May, six months after my surgery, I finally got the fill that made the difference. I started losing about 10 pounds per month for a good seven months. The weightloss slows as you start getting closer to goal. So far I've lost 115 pounds with about 20 to go. Don't go into this expecting the quickest fix. When I started I thought I would be at my goal weight by May, not just starting to get restriction. And even with a good fill level, when i stall for a few weeks, I still get that panicked feeling that I will no longer lose weight. That's when I tell myself "remember when you weighed 290 and didnt think you would see 289? Remember when you were at 276 and didnt think you would get to 270, remember when you were at 226 and didnt think you would see 224?" I keep reminding myself of all the times I thought my journey was over only to lose more and more weight later on. For me the weight loss isn't consistent- it could be 5 pounds one month, one pound the next, none for a few months- and you really just have to go with it. Don't stress when you're not losing- it takes your body a while to shift everything around.
My last bit of adivice- take before pictures!!! Even though i was incredibly embarrassed at the time I took pictures at my heaviest weight, and boy am I glad I did it! I took them straight on facing front, facing back, and side view. I've taken pictures once a month since, as well as keeping measurements, keeping a journal to write about how I feel during important milestones, and tracking weightloss (i put in what i weigh on the last day of every month to compare). Now when I'm feeling bad or like I havent lost anything, I compare my current picture to my heaviest weight picture and it just blows my mind. When I put the two side by side I no longer pick at what I have left to lose, instead I marvel at how much I've lost. I was recently worried about the currently fattest part of my thighs until I noticed while doing my monthly measurements that the fattest part of my thighs right now is the same size of the smallest part of my thighs back when i first started. If that makes sense, right now the biggest part of my leg (thigh) is the same size as what was once the smallest part of my thigh by my knee. Do as many measurements as possible, this really helps to track what and from where you're losing fat. Measurements are far more important than what you weigh on the scale.
My ONLY regret with this surgery is that I didn't have it done sooner- yes I've struggled with food since banding, yes I miss certain foods, yes I've eaten things I shouldn't, yes it's been physically, emotionally, and mentally tough- but now I can walk up stairs without getting winded, I can fit comfortably in seats at movie theaters and on airplanes, I no longer wear sweatshirts even in the summer to cover up my extra flab, I can look at myself and not feel disgusted or shameful. You have a great opportunity in front of you and I wish you the best of luck on your journey!