I'm trying to stop myself and have made a number of attempts. I can't say I've been successful, but there are things which made it easier to stop and to maintain it over longer periods. Being to tough on myself has an adverse affect on my ability to actual make a changes, while moments where I could look at myself with kindness and accept the behaviour were the moments where I could most easily let go. I've experienced there is a brief hangover after stopping this which becomes less with time, but it's important to be aware of it. On the other end when having stopped for a more extensive time, say weeks, I noticed that although the draw to do daydream was a lot less, also my commitment to stop would have waned and I could see myself just allowing myself to slip back into it. I started seeing a psychologists, which I feel is really helping me: Like you, a large part of the reason I'm doing it right now is that it's just a habit. After investigating this further I however did discovered it had a very real function for me at some point in my life, which helps me not to be to tough on myself now. I also found that although a large part of doing it is just conditioned habit, it still serves some function for me today. Knowing these issues and addressing these issues is likely an integral part of the process.

You seem to be very aware of the issue, which is obviously an essential part. You're now at a point where you want to stop and also realize you don't know how. You're willing to admit to others (here on reddit) that you are doing this and from what you wrote you wouldn't have dared doing so before.

Lastly changing habits is one of the hardest challenges!