Challenging My Negative Thoughts

I'm terrified that by acting inconsistently when ewan challenges me and I get angry, I am ruining Ewan's attachment to me. So much so that I spend the time after a hard bedtime beating myself up. My punitive voice being cruel and vicious;

You are never good enough.
You deserve to feel awful.
You were wrong to get upset at him. He is 3, you should not shout at him.
He will end up miserable and depressed because you will end up as bad as your mother. He will never be securely attached and have a terrible life because you cant handle him being angry and incredibly testing.

I am good enough and exceed expectations *most* of the time.
I deserve ti feel proud that I was as angry as I can get but I didn't hit or use my body to inflict pain.
Yes, he is only 3. Shouting at him is counterproductive and not the best choice BUT sometimes all you can do is be good enough.
I am consistent with him most of the time, it's only when I choose to get angry that I make bad choices and fly from angry, to bargaining, to sad, to angry, and all around again.
If I am a good mother most of the time, then how I behave when I am angry can be forgiven. I have to forgive myself.

Reminder: my mum was never a decent mother. She played the part sometimes, but she didn't mean it. Like a shoddy actress.

I've had to gain an insight into attachment theory because it is part of who I became at the hands of my emotionally neglectful mother. But that knowledge is another reason to berate myself, when I do make a bad choice.

Becoming angry isn't the child's fault, I become angry because I am not very good at regulating my emotions. I'm trying to learn, I don't want to snap back and forth and all over the place, I want to be calm. I just don't know how.