not a good thing that u react like that, these things do happen (as u well know). obviously u have been really angered and provoked within ur relationship with this person.
i have been like that and 10 times worse with my exbf, i was so ashamed by the evil twisted things i said and did to him and swearing at him etc because i was so fed up, hurt, angry etc. and i know what u mean when u say u become like a monster possessed.
i havent read all ur other posts on this, so dont know how often this happens and if its with the same person or different people. if it is the same people time and again, perhaps u need to get them out of ur life as they are a negative influence and making u react in this way.
as i said i didnt read all ur entrys but just wanted to say do not be so hard on ur self mr H. your only human, we all make mistakes. and the thing is even tho u have said and done these terrible things, u are aware of the issue and u want to try and make it better. so thats good that u can acknowledge it and be aware of it and try to make it better. for this and any other negative issues in ur life, u also have lots of positives things about u (from what i can see from ur goals).
so just be strong, try to be calmer and aware of ur self when ur in that negative zone if u can. i hope things get much better and the negative behaviours go eventually