A few techniques to break the cycle of anger in a relationship consist of doing something out of character.
An example would be to intentionally slow down the process by going for a walk by yourself. Try moving your body or give yourself some space. If needed, take a weird or unreasonable action; laugh where you would usually cry or swear, and most important try to imagine a peaceful scenario.
The most important is to try to do something out of character at the precise time that the anger breaks out.
Do this routine every time the situation arises.