How do I control my anger in regards to this decease? I'm heading down a dark path that I fear will lead to bad things

I've had this decease for a few years now and been doing pretty well.

My hb1ac has been between 5.3% and 5.6% during all my years. But as the years go by I got more and more angry when my blood glucose goes high or low.

I've started to harm myself in various ways just to do something with the anger. Not cutting or anything like that, but things like punching myself on the arms, or punch walls (hurting my knuckles) etc. I got like 3-4 bruises on my triceps right now, from punches or insulin injections (I sometimes inject into the muscle to have a faster insulin reaction).

I know it sounds crazy but it feels better than just letting the anger linger. In some cases I can get angry at myself which makes sense (like if I miscalculate the amount of insulin to take). But in other cases I know it isn't my fault (cases where my "analysis" on how much insulin to take made sense, and I wouldn't change it even in hindsight, yet I go high or low), and that's maybe even worse because then I don't have anything to direct the anger on.

Honestly I feel like I'm heading down a dark path sometimes. I'm not suicidal, and I'm not depressed, but I wouldn't be surprised if I'm not here in five years or so when I extrapolate the path I'm heading towards.

I just don't know what to do. My doctor praises me every time on my good blood results and I'm doing good in other parts of my life, but the anger of occasional bad blood sugars just consumes me more and more.