I'm with the others. I've never known what people meant when the say it takes XX days to form a habit.
I think there is something to the idea of if you do something more often it gets easier. All the research in cognitive psychology backs that up. But that doesn't necessarily mean those old habits have been kicked to the curb. I didn't exercise regularly for nearly 40 years -- that's an ingrained habit for sure. I've been exercising for nearly 2 years now, and it's still a struggle to make myself do it. I have actual conversations in my head when I'm thinking of going to the gym "Yes, Heather, you're tired/overworked/too busy/achy/whatever to work out. But you need to do this and will feel better later." At least I listen to myself these days! Maybe in another 38 years...
What does get easier is knowing WHAT to do and how to manage different situations.
A lot of my daily eating is on automatic pilot (provided I stick with my plan). I know what to shop for, how to put together breakfast, lunch, dinner, snack combos, and even how to incorporate eating out into my plan.
While it's somewhat automatic (which may be what a "habit" is) that doesn't mean I can let it go on it's own. I have to be conscious every single day of what I'm doing or overeating easily (way too easily) sneaks in. Even overeating healthy food will stall weight loss, after all. And again, after nearly 40 years of NOT doing this... well, those old habits are waiting in the wings...