I decided to quit sugar when I learned that it was the main reason for my acne.  First I experimented with quitting sugar for a week to see if acne would clear, it did.   I have tried limiting my sugar intake before by not buying any sugar products and only eating sugar if it was offered to me for free, but this quickly fell apart because I would be simply too addicted.  So using clear skin as my main motivator and concentrating on that, I decided just to quit once and for all. 
I thought about my highschool english teacher who was allergic to sugar.  I thought about how back then I felt bad for him, but now I wish i was allergic to sugar.  Thats when I had my brilliant idea: why can't I be allergic to sugar.  From that thought on, whenever I came across a situation where I was offered sugar, I would tell them that I was allergic to sugar.  Since these situations came often I pretty much told everyone I was allergic to sugar and couldn't back out without getting caught and looking like liar.  
It worked.  I quit completely and started telling the truth instead: "I was telling people i was allergic in order to quit sugar".  My friends found it humorous that I took such extremes to quit and was shocked that I wanted to.  I no longer needed to lie to them and telling them what I was doing had the same motivational effect as telling them I was allergic since I was already a month in.

A few tips and pointers:

I've found that a good substitute for dessert is an Americano (no sugar added) with a little bit of milk.  The milk helps the bitterness of coffee.  But now I just drink it black and it tastes good. Also, Tim Ferris talks about a method where he binges and then downs a cup of coffee after.  Apparently coffee somehow mitigates bad food.   I have tried it after a sugar binge and found that I did not gain acne the next day.  

Also, think about how much money you save by not eating sugary snacks.  Allow yourself to buy good food from nice restaurants whenever you want from that saved money.  Tell yourself, I can eat gourmet meals now because I don't eat sugar.