The pain and loneliness that you are experiencing can be lessened by a multitude of things.
1. Wait some time. As impossible as it may sound, it is a fair possibility that you and your ex need to cool off a little. You should distance yourself from you ex unless the situation cannot be avoided. These unavoidable situations include working at the same job or going to the same classes. Thinking that you can just be friends won't help get your ex back or fill the void that is left in your heart.
The old out of sight, out of mind is totally true in these cases, avoiding contact is the best way to begin to forget. Distance can make the heart grow fonder.
2. It's time to party! There's nothing like hanging out with your closest friends and even for several straight nights can be just what you need and make you forget a good portion of the break up pain you're feeling. Get a group of friends together and have a fun evening. Don't turn to alcohol, it will only make matter worse.
3. Girls will take notice of you and your friends while you are out enjoying yourselves. Don't worry, this is perfectly ok. There's no need to feel guilty about this, in fact, it's good to enjoy the company of hot girls. The good thing about books of this kind is that after reading them you are kinder to yourself and becomes braver to face the world on your own even as you feel you are ready for someone else, a better partner.
Dating them is certainly not a requirement, but flirting and enjoying hanging out with some hot and sexy girls can bring your life up a level to not feeling as bad.
Make a list of all of the things that you could do that would help you get over the pain of your break up. Finding a new hobby, working out, a night out with your friends are great things to do to help you deal with the pain, but they are also great things to do to get your girl back. If you are looking to have your ex back in your life, please look at the link below.