I'd say the ease which you can pick up habits or drop them is extremely variable across the specific habit and person. (as a different example, someone with less social awareness will find it harder to pick up the habit of being a hospitable host than someone it comes naturally to, but once learned its probably fairly easy to maintain)
One of my favorite quotes is, "first the man makes the habit, then the habit makes the man" , and it works both ways, good and bad. I really think this is something that should be taught much more explicitly in school to everyone, rather than leaving it only in places like sports and the military.