I need help with this too, Its very hard for me to stop that feeling because usually it comes on so fast there is not much I can do. There have been a few times when it starts more gradually. If i feel like i'm starting to lose some control, I try to get some ice cubes and hold them in my hand, sometimes it helps keep me in the moment. I've been doing this since I was a kid and it seems to help. I know I really need therapy but I haven't been able to actually talk to a therapist yet. Hopefully soon. I'm so embarrassed by the flashbacks, its held me back a lot and I'm always so afraid its going to happen at any moment. Most people do not know what I have been through and I always worry because I don't want anyone to know. I have severe social anxiety and its hard for me to even go out to the store because of it. I really hope this gets better.