Its always a good thing to have a heart to heart talk, especially on serious issues like this. Others may not always understand how you feel or think on a particular situation . . while I feel the plastic knife may not mean that much, she probably didn't know it was devastating to you - it could probably just be a little joke. Ask her for some time to talk, and let her know how you feel. You're close friend safter all, and by doing so you not only clear things up, but you'll strengthen the relationship as well . . So in the days up till thursday, perhaps you might want to find some time to relax and quieten down before speaking to her - - plan early . .
Its also great to know that you are able to fight that urge - thats probably the biggest step in getting out of the problem. . . Eventually it comes down to your own mindset - but for now getting her support will help you a lot . .
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The key to victory is the element of surprise.
When that doesn't work, I guess I just gotta gun you down.