1. No matter how much you hate the guy, keep quiet. Being hateful or coming off as jealous isn't going to help you, in fact it's probably going to make her think it's best she's not with you anymore.
2. Your heart is going to tell you to call or text her. Don't! As hard as it is, you have to give her space. If you’re readily available and she knows it, you’re just blowing any chance of making her miss you!
3. NO begging and pleading! This will never work and even worse will make you seem crazy or infatuated and you really don't want that or the embarrassment that comes with it!
(If you’ve already done some of the things mentioned above don’t worry we all have at one point or another, just try to focus on not doing them again in the future. How you react after a break-up will be the determining factor to whether or not you’ll ever have a chance with her again.)
Here is something that should keep you thinking positive: That time you spent with her is only a very small fraction of your entire life, so what do you think the chances are she's going to be with him forever?? These days, SLIM to NONE, especially if they’re still young! Forever is a long time when you’ve only lived ¼ of your expected life! Don’t go wishing them bad luck though or you might find karma coming back to get you. Just relax and wait. The odds are in your favor without you doing anything at all.
The most important advice of all is to keep your head up and keep living life! Never let anyone hold you back. Sure it’s painful to know she’s with him but time heals all wounds if you let it. Don’t let things make your life miserable and keep you from achieving your goals, use your emotions to fuel your motivation! Become the best you can! Maybe you’ll see her again; maybe you won’t, either way you’ll need to be at the top of your game so you’re ready for anything!