For me I was eating a raw meat diet that i would also eat candy and cake and shit like that on the weekends. Then my wife and I had what we refer to as "Choc-Mint Weekend" where we stayed home and pigged out on a bunch of bullshit and felt absolutely horrible. That night we came to the decision that above all else, we really enjoy having a good time and if you're not feeling absolutely 100% awesome, then you cant be having a good time. Thats when we cut the last (major) addiction and went 100% carnivore diet and havent looked back.
We still check out the junkfood in the weekend fliers but its more so we can eat it in our dreams, we both still have no real desire to eat it again.. Its the memories we love, the reality of it is more

I suppose i didnt answer the question here.. I added raw meat into my diet at the start of the year but still ate veggies and fruit (although i cut waaaaaaaay back on my sugar intake, id go through over half a pound of honey in a week... just honey, not including the pounds of dried fruit and stuff i was eating.. I mean our bodies run on sugar, right!! its healthy sugar!!) then we cut veggies out because it just started making sense that they werent food (now i cant even bring myself to eat stuff from my garden i started this year, and i WANT to eat it.. i just cant fight my NO instinct i get now haha)
So i cut veggies out, ate candy instead, then said 'you're a retard, what are you doing to yourself, cut the shit' and havent looked back since the 'withdrawl' period that lasted mabye a week or so, but i guess when you understand that its just an addiction and analize it, you can deal with it a lot better, i personally didnt find it very hard at all to do once i made a firm decision to take my real health first.