It is difficult to keep myself from repeating the problematic thought patterns. I try to keep myself distracted to ward off the effects they have on me but the core issue is still there, only subdued. I've tried, arduously to get rid of these parts of my psyche and I do not see them going away upon sheer willpower alone. Whenever I drink they're less apparent but if I were to use that as a means of change in my life, I'd become an alcoholic. I know Marjiuana helps but in that case I'd have to fork over so much cash that I simply do not posses. There's no chemical solution to something like this as a Hikki in most cases, which is one of the main differences between us and normies. Normies drown out habits/problems like this through substances we lack the means to acquire.
So it all comes down to you. I've always thought that if you repeat to yourself an ideal of who you want to be, when visualizing it enough you become that ideal. Such is not ALWAYS the case for becoming a normie when you're a Hikki but it does work on smaller things with enough concerted effort. If you want to for example stop thinking about a memory you have that was embarrassing the way to go about this would to be first, reconcile the existence of that memory by speaking about it to someone else (even in text this is helpful though I'd recommend verbalizing it to yourself whilst/after writing it). Through anonymity you'll be able to get this off your chest with virtually no repercussions. The second step in this equation is more tricky. It's learning the ability to appreciate what is happening now vs. then. It's unlikely that the mistake will be made again. The way I internalize this is by telling myself "I accept whatever has happened because in the end it made who I am now and I'm proud of that". That seems like a massive undertaking ideologically for many a' self loathing hikki but hear me out here.
If you can find pride in something about yourself, anything even if that pride is facilitated by putting down others you're on a decent track to some form of confidence. From here one must continually repeat those positive attributes to oneself until you BELIEVE that you're good in some way. And trust me when I say this, believing it sincerely in your heart is extremely important. If you can make a positive image of yourself then it will be easier to accept the past as something that is ended and can be moved on from.
Self-acceptance may not be easy in a state like this but it helps to find the good things in withdraw and while focusing on those to also focus on how negative the outside world is versus comfy life. Making a value judgement that states Hikki life is better is a good way of accepting the life style. You see, you can't accept yourself without accepting the life style and you can't make any progress without having that sense of confidence and pride in one's self and abilities. Something as simple as believing you can make it is all you need to put forth action.
Bruce Lee was able to act because he continually visualized who it was he wanted to be. That form of repetition of one's goals, of visualizing the ideal self, and of garnering confidence in who you are will lead one to success in some form. It may not lead us all out of here but we don't always need to be lead out as I said.
So to answer the question in the beginning (I got a bit carried away with the caveats of everything involved), yes it is possible and can be done through (to put it in rather normie terms) believing in yourself and by putting practical methods in practice.
If you're seeking to break a habit first I'd weigh the pros and cons of breaking it, ask why you want to, and then from there fill your life with other distractions in times/places in which you would normally indulge in that habit. From there I would seek to replace it with a more positive one like writing (which you should've already been doing for your health). Reward yourself for those efforts, don't feel too guilty when you fail, analyze how you failed to do it right next time, and keep at the assertion that you are capable of making it because if you don't sincerely believe that you are capable of this task you might as well not even try.
Monks and religious hermits throughout time were able to act with immense control over the body and mind, they were at peace despite being closed off from the eternity of the world outside their monasteries. They faced the freezing cold through sheer acceptance, control. Literally their bodies experienced less adversity in the freezing cold because of how the control they had over their brain. Alan Watts spoke about this in one of his lectures. It is possible for the mind to go great lengths with the right fortitude. I believe in my fellow Hikkis to make that leap as I am also trying to.
I recommend watching this video also: https://www.youtube.com/watch?v=hQ2XMKHsg9I
I wish you well.