Broken Hearted Forum - Devestated Over Breakup

Hi,..I am new to this site and may not be in the right forum. I apologize if this is true. I'll keep it as brief as I can. I was involved with a woman for a little over a year. It happened very fast. We only had a few dates, but we seemed so compatible, things felt so right and moved very fast. It seemed we had so much incommon. The physical attraction was definately there, and we seemed, intellectually, a very good fit. We were both in our 50's she 54, myself 50 when we met, not kids by a long shot. We fell in love very fast. My girlfriend was diagnosed with clinical depression before I had met her. I took it with a grain of salt because things were going so well, and I was ignorant to the effects of clinical depression. A short time into the relationship, I noticed definate personality changes. She would have unpredictable mood swings,..crying spells, to anger, and mixed moods in between. She was fired from 2 jobs in less than 3 months. Not to mention the 2 or 3 very well paying jobs she had lost before we met. No matter how hard I tried to be there for her, I would be the target of her mood swings, and paranoia. She would be paranoid of the neighbors, telling me they were conspiring against her. She was refsing to take her meds. She was also smoking a lot of Marijuana. She said it helped her with her depression. She was also on pain medcine called Ultram for a lumbar problem. She was on that for at least 5 years, and I felt she was addicted, but she would argue otherwise. Her doctor also put her on Adavan for her anxiety. I went through rough times with her,..but because of my feelings for her, I was willing to stay in the relationship. In an 18 month period we must have broken up and got back together 5 times. There were times when things were going so well, and she would just change, and yell at me for not being able to communicate with her. We broke up for good, right before Christmas 06'. She became so unstable, it was like walking on eggshells to be around her. I initiated the break-up, and felt very bad about it. In Feb. 07 I sent her an E-card for her birthday. She sent me a very brief thank you reply. That was our only communication, although I wanted to call her. It has now been 3 months since we broke up. I am still grieving. I feel like I have failed, and shouldn't have abandoned her. It's hard to deal with. I feel guilty for arguing with her when I should have been more understanding. Are these feelings normal? Thank you for reading.