Not the same thing but, my friends and I have a pity party then a wake then a bonfire, after the break up of a long term relationship or a situation where we felt we didn't get closure.
This is of course not as simple, since you don't share this kind of thing with people, like you would a marriage break up.
But I think there is a lot to be said for allowing yourself a grieving process, then the opportunity to give thanks for what good there is in our lives.
As for burning things...fire is symbolic of cleansing, also once those things are alight you can't dig them back up again.

Don't get me wrong I don't believe this is the answer for all.
And betrayal by your T is on a whole different level.
But it's just a thought.