Love keeps me up, and it also keeps me down

Have you ever had a partner that you absolutely thought was the one person that you could not live without?? I have...I started dating this girl Courtney last summer in June, we were the perfect couple for about eight months. I started losing sleep and i became angry at the world and i found myself taking it out on Courtney. I never hit her or touched her in an aggressive way, im not that type of person, i would have let her beat me with a bat and i wouldn't have retaliated. I just became angry because i wasn't sleeping at night and i blamed her for it. Well when that final month came around, i went to her house and walked into her room and began explaining that i was unhappy with her. The truth is, i was unhappy with myself, after i broke up with her i haven't smiled since maybe January 14. I lie down on my bed, close my eyes and try to sleep but i never sleep, i just see Courtney and i replay moments when i was with her. She started dating my best friend 2 days after i broke up with her and i keep blaming myself for everything that has went wrong in both of mine and Courtney's lives. I feel like i made the worst mistake of my life by letting her go. I still love her and i would give anything just to hold her again. my life was complete when my arms were around her. =/