How can I stop being triggered?

How can I stop being triggered every time I think of, or hear something to do with his wife? This has been going on for over a year now (the situation between us) and it's only getting worse. Every time his wife gets brought up even vaguely, or i think of all the years that she's had with him, I feel absolute rage and despair.

I know this isn't good for the process, never mind how awful it feels. I know that I need to get past this, but how? How do I even begin to get towards acceptance?