There aren't any habits I ever regretted. (My kids are grown now.) The thing with such habits is this: Children outgrow them. They either outgrow them on their own, and sooner than parents had thought they would; or else, they get to be an age when they're old enough to understand words like, "Now, you're kind of big to be doing this, so let's think of something else to do." When they're at one age and really in need of one thing or another, they actually do need whatever the habit is. Then, they get a year or two older and no longer need it. That's when it's not needed but just a habit, and that's when they're most often more ready to change the habit.
One example I have is my son, who used to ask me to leave the bedroom light on until he fell asleep. I didn't see it as a big deal, so I did. Since I didn't want to go to sleep, myself, with a lamp on in his room, I'd shut it off before going to bed. One night I went to say "goodnight" to him. As I started to leave he said, "Would you shut off the light?" I said, "You don't want it on?" He said, "No. I want it off." So, while he'd needed the light on when he was five, he no longer needed it on when he was seven. As far as I was concerned, if he wanted the light on until he was thirty it was his business. MOST of the time (I'd say pretty much all of the time), kids just outgrow things and decide they don't want to do them any more.
I guess the advice I'd give is for parents to pay attention to when it is the child seems beyond his/her need for whatever the habit is, and "capitalize on it" (or on some change in routine that may offer a good excuse for a change in the habit). When my kids were little I'd let them fall asleep on the couch in the living room, and then I'd carry them to bed. When preschool and/or kindergarten came around I said, "Now that you're going to school you have to go to sleep in your bed every night." I was effortless to get them to stop expecting to "do the couch thing". I think too many parents worry that little kids will do whatever they're doing "until they're 30". They don't. Each year they mature, and their needs, fears, and insecurities change as they do. Something parents might want to do is read up on the different needs, fears, and insecurities of each stage of development.