You may have fought back and feel guilt over this instead. Maybe you feel you made the situation worse or maybe someone else got hurt. Fighting back, like freezing, is not a choice you made - your body decided how you reacted and you are not to blame for anything that resulted from that.
The other thing that many survivors tend to do is to look back and see all the things that they could
have done to prevent or change what happened. What you are actually doing here is judging the situation as you see it now - everything is easy in retrospect. However you did not have the information you have now at the time you were raped, abused or assaulted.
You did the best you could to survive in the circumstances at the time. For more information on the body's biological response to fear please see Aphrodite Matsakis' excellent work on PTSD. Details of her books can be found on the Books page