I think you should take it one day at a time. For example, if you eat McDo about 5 times per week, spend a week eating it for just four days.
It could be like this:
Week One: Have McDonald's 4 times per week
Week Two: Have McDonald's 3 times per week
Week Three: Have McDonald's 2 times per week
Week Four: Have McDonald's once per week
And while you are cutting down on the McDo, introduce healthy foods into your diet. Apparently you like fast foods, so to go cold turkey will not work. Just try to slow everything down and create new habits one day at a time.
You could do the same thing with cleaning your house:
Week One: Clean one day per week and then be messy
Week Two: Clean two days per week and then be messy
Week Three: Clean three days per week and then be messy
Week Four: Clean four days per week and then be messy. But by then you will be used to being a bit cleaner.
If that sounds too hard take it even slower. Turn "One Week" into "One Month". Yeah I know it sounds like a long time, but if your habits are really bad, you need to set goals you know you will achieve. It's important to feel good about yourself and you'll feel great when your achieve goals.
Think about it. Wouldn't you rather develop healthy eating habits and become neat in fours months or would you like to continue the way you're doing things now? For some people this method sounds Super Slow, but again it depends on how bad your orginal habits are.
It's like when people quit smoking;they quit one cigarette at a time.