I see that you are struggling with something that most people in the world struggle with. it is said that the heart and the mind are the two things that are the furthest from from each other. If im not mistaken i think the “malbim” in the begining of “mishlei” says that the purpose of mashalim are to bring concepts down to the heart. This a very big tool in limud hamusar to help bridge the gap between your heart and mind. You can for example use this tool in your situation by visualizing if G-d punched you would you get upset at Him? I dont think so (at least i wouldnt)… then ask yourself why you get upset when he sends a shliach to punch you. by constantly visualizing this it could help you internalize this concept of emunah. you have to use a mashal that works for you!!!!! it should be noted that you should do this work way before you get angry maybe even set time aside every day to to visualize this. with the help of hashem you should be zocheh to reach shlaimus.