I know the feeling, all too well. It's good that you have not acted on these feelings but I can tell you that your stress and your guilt are merely feeding the fire to drive to to act on these impulses.
What has been effective for me is to find a good friend and hash out whats going on in my head. Sometimes that will alleviate the pressure enough to stop the thoughts. Other times, it's just as your signature says -- breathe. I learned at Alta to take a few deep breaths to get grounded, and really think about your breathing. Instead of breathing involuntarily, breathe voluntarily. See if that brings you back to earth.
I don't know when these types of thoughts will subside. I do know that I have a full range of self destructive thoughts on a daily basis. They can be very difficult to deal with at times.
All the best,