I've been dealing with this sort of thing for too long as well, and have tried so many deflective strategies they'd form a small mountain. With me they also tend to happen at night, and have ruined many an attempt at sleep. So that's the bad news.
Only in the last couple of years did I come across the notion of acceptance. It's easy to dismiss that as 'what...allow what happened?' No, that's not it at all. What one is allowing is the understanding that thoughts are
only thoughts, and they will come and go. Some are awful, some better, some good, but trying to totally control or defeat them gives them power...like someone saying 'don't think about an elephant' for the next 5 minutes; and you can't stop the thoughts.
BUT they're still just thoughts. Some of them stem from memories one would like not to have, and it's grievous to ever have them again. But then--they will pass through. Brutal as they can be, they are also invitations...to heal. This sounds almost self-defeating, and I've been there so often, wanting the quick fix for thoughts...which will still pass on their own no matter what I do.
But acceptance is only the start of it. I also realize that the thoughts represent the
old story, not the present. The best metaphor I've heard is that of a life as a movie screen. The empty screen is like one's consciousness. On it are projected images (thoughts) that can range from horror to comedy. While the movie is running, it can be frightening as one takes it all in. Then the show ends, and it's NOW again, and now is one's only true present reality. One can, and does, still grieve or tremble or react to the story they've seen, but the realization/acceptance is that the story
IS indeed over. Despite the thoughts; but they will somehow find the exit.
There are ways to aid the process. My favourites are a short meditation where on the in-breath I say 'peace', on the outbreath 'love'; and I have a huge batch of music which, if it doesn't chase the memories away, brings soothing that I need to realize that yes, those are 'just' thoughts. I may have them again, I may cry, be in pain, scream, etc. I can grieve them, fight them, and still accept them; but if I accept them I remember the other part of acceptance--that the thoughts DO go away.
It's very disheartening, these thoughts/memories/flashbacks; it's also senseless and cruel to have to accept, to even have techniques of escape. Why me and all that can trigger me big-time mentally and physically (asthma especially). All I've learned, and of course this is just me, is to realize thoughts do come and go. But I need to relearn it all the time, it seems

. Try as I might, I will never find a reason it has to be so hard; but that's beside the point. At least I know I'm in a safe place now; that's all that matters, NOW. When we accept and allow that to sink into our being, we realize we are beautiful beings as we are and don't have to wait for it--no thought can take that away anymore.
