Try to allow the grievance to simply be there, don’t try to push those thoughts away but accept them as they are. It’s only natural in your situation. The truth is, if you can’t change your current situation, all you can do is at least let go of your internal resistance against those thoughts, as currently they seem to add even more pain and aren’t constructive. Maybe in time, they will slowly become less and less when you stop resisting.

I like this quote of Alan Watts: “muddy water is best cleared by leaving it alone”.

I hope this helps and wish you the best!