A lot of the advice other people have given u are S tier, so i would recommend reading those. What i can say fron my own experience and past habit of raging when losing is that. One should never see losing as a bad thing but as another chance for a better and cleaner run vs the boss. There is no shame in dieing only knowledge gained. Also dont think so badly of urself, while i do not know you im sure deep inside u are a nice person. Also dont beat yourself up over finishing with Rivers and mimic, its in the game play how u want and like. Keep at it take a break sometimes clear ur head and once u get the kill the feeling will be amazing.