In the beginning there was darkness. But after a certain period of time, filled with mood swings, struggles, mental fist fights with miss Sugarmonster and maybe a slip or ten, after forcing yourself to stay on track - you will see the light at the end of the tunnel. And suddenly you are there. Still far away from your goal, but you have reached the light. The light where it is no longer a constant struggle to keep on trying but rather just goes automatically. The light where you notice that you actually don't really feel like trying the cake at work because miss Sugermonster has given up. The light where you actually long for kicking some ass at the gym because you know how great it will make you feel afterwords. Suddenly you are not trying to convince yourself anymore - you are just doing it and you start feeling that you can actually manage this, for real!
It is worth going through the torturous phase to get to the light. And really - it does not take that long. I have a three day rule. That is how long it takes to get past the worst of the cravings. The diet is easier after about a week. After two weeks you'll probably be in the flow, you've gotten the hang of what you can eat for your different meals, the sugar addiction is on hold, it is not a huge mission to get to the gym anymore and you're probably starting to see your first results.
I read somewhere that it takes three months for a new habit to get established. Might be true. Probably is. But it will not be a constant fight trough all that time. The fight is only in the beginning. I believe that you will find your health salvation within a month. Just give it a try. A real wholehearted try. You can do it!