The key is moderation.
Through 2006, my day wasn't complete unless I drank two liters of Coke, ate loads of fried and sugary food for all of my meals and snacks and finished it off with a half-box of ice cream. I'm 6'4" and at the time weighed 318 pounds so I wasn't in terrible shape, but I had a health scare and decided to turn things around for myself.
I went cold turkey and cut out all sweets, junk food, fried food, heavy breads and sodas. Yes, I did say moderation is key, but my diabetes scare(that luckily turned out to be low B levels)prompted me to act quickly. I started cooking all of my meals, eating primarily grilled chicken and fish, mixed vegetables and moderate amounts of beans or whole grain brown rice for carbs. The only things I would drink were water and protein shakes. I absolutely hated my meal plan at first, but I stuck with it because I was extremely determined. The worst thing was the sugar craving, I was used to having soda throughout the day, candy for snacks and a huge bowl of ice cream with syrup, cool whip and crumbled Oreos every night. Substituting apples and bananas outright sucked, but I stuck with it.
After sticking with this plan for a while, I learned that I could treat myself on occasion without penalty, so one night a week I would eat a hefty meal at a restaurant with friends or pick up fast food from somewhere(almost always Chick-Fil-A), then have a small bowl of ice cream for dessert. Moderation.
I began changing out different proteins and vegetables every few weeks so I wouldn't become bored with what I was eating, trying out different recipes, etc. Eventually, my cravings subsided and portion sizes diminished.
I have stuck with this for over five years now without fail. I lost over 120 pounds and have never felt better. I cannot stand the taste of any soda, I don't care for candy and the majority of ice cream/cookies/cakes/etc. just tastes way too sweet, so if I eat any it is in small amounts. I work out daily(currently building up for Tough Mudder), eat what I want(still very healthy) and kicked my cravings to the curb. It's a great feeling.
You can do it if you are determined, practice moderation and realize that it isn't a diet, it's a lifestyle change. If you reach your goal and quit, chances are you will end up right back where you started.