While most guys who are worried about losing face with their friends might not want to admit it, there is an even more powerful feeling than the anger you are experiencing, and that is the sadness that comes with it. While anger gives you energy (although it is negative energy, of course), sadness is simply a debilitating feeling. When you are really sad, you do not want to eat, you do not want to go do anything, you simply want to lie around, sleep, or feel sorry for yourself. Hell, you may even do all three!
Breakups are very complicated events and thus, lead to a lot of different effects. You can also expect to feel confused, mostly because it is a very sudden change that you will not have seen coming. Overall, you just will not feel like yourself for a while.
One last, but very important note:
Do not do anything to harm yourself or anyone else.
Your goal here is to win your ex back. Your goal is not to make her feel bad or realize her mistake by taking your own life. Your goal is not to beat the crap out of her new boyfriend (though you might be very tempted to do so). This will only make her feel closer to him, and more distant from you. Your goal is not to hurt her, no matter how angry you are. In fact, if you feel angry enough to do physical harm to her, do yourself a favor and move on. Obviously, there are a lot of issues within the relationship.
Our strategy here should provide positive results. You will be a better person if you follow these steps, and your ex will appreciate these changes. You will ideally win her back and restart your relationship on the right foot. If there is another guy, you can hurt him in the best way- by winning your girlfriend back and making him feel the way that you feel now. Nowhere in this strategy will it be suggested that you hurt yourself or someone else physically. That’s because it would be flat-out stupid to do so, and will not help you achieve your ultimate goal.