You need to stop feeling sorry and blaming yourself. Most of the times, a breakup is inevitable and unavoidable. You can't beat yourself up over something that was not in your hands.
It is common for people to bad mouth their former partners. However, you need to be dignified and respectful, even after the break up. Respecting the other person will in turn make you respect yourself more.
Sit yourself down and give yourself a talk. The only person running away from all this is you, and you need to look into the mirror and tell yourself that it is over.
Don't become a recluse. Isolating yourself from others will only harm you. While it is natural to want some time alone after a breakup, you should look to meet friends and have a good time to get your mind off things.
You might want to avoid any mutual friends the two of you have. It is also natural for mutual friends to split and form alliances, but you should stay away from all that drama for as long as you can.
Get closure, do not consider this as a break, take it like a breakup where things will not go back to the way they were. This will help you move on, rather than suffering in uncertainty.
If you two were living together, return his/her belongings and don't keep mementos. If you really do want to be over your ex, you will have to get rid of anything that may appeal to your sentiments later on.
Initially, you should look to avoid the places the two of you visited together. Don't hang out at the same bar, club or restaurant and look for new hangouts.
If you call your ex after a breakup, you will end up regretting it. There is nothing more humiliating and embarrassing than showing desperation to your ex, who probably doesn't care anymore. It is best if you remove his/her contact information from your phone etc.
Take up a hobby to distract yourself. Joining a gym may be a good idea, allowing you to vent and remain in shape to get back in the sea.
Occupy yourself, be it with work or entertainment, to avoid having too much spare time on your hands to think about him/her. There is no use reminiscing about the past.
You can go on a vacation with your friends and family. Time away from all the mess will help you focus again. The vacation will also serve as an opportunity for bonding with those who matter the most to you.