It never works to completely ban something from your diet plan.  It’s not like smoking where you really should just go cold turkey.  You have to take time, and frankly there are steps to be taken so that eventually you don’t want that much junk food anymore or it just fits right into your diet.  First of all, you have to reduce the amount of junk food you are eating.  Don’t completely eliminate it, just tell yourself you can have this much per day and that’s it. 

The best way is to actually tell yourself that you are going to eat clean during the week and then assign yourself one cheat day per week or cheat meal in which you can eat some of the foods that you love, in moderation of course.  This will help you to gradually step down without running to the problem of cravings that hit whenever you tell yourself you can’t have something all together, they get stronger.  Then replace these with foods that provide you with maybe a sweet taste that you like without all the calories.  For example try grapes for a sugary taste and they are completely healthy sugars and it only is 100 calories per 100g.  Over time, your apparent need for these foods will lessen, and you will see greater benefits.  It will just take time.