I'm very sorry to hear about your loss. I can't say I understand exactly how you feel, but I once had to give away one of my pets for good, a cat that had been with me for a long time. I felt horrible in the beginning, and kept feeling bad for weeks afterward, knowing I wouldn't ever see her again.
There's not really all that much you can do, I'm afraid. Just try to accept the fact that this happened, and try to move on with your life. If you get too depressed about it, I'd recommend seeing someone, not necessarily a psychiatrist, but just someone you can talk to, whether that's a friend, a significant other, or a relative.
I wish you luck, and I hope you're able to deal with your grief.
