Hi Kimi,
I know what you mean about having a down day...
It's been eight and a half months since I last saw my Qorqui alive. This morning I was looking out the bay window in our den and I noticed the scratches in the wood where Qorqui would jump up and look out "her" window. I fell completely apart. I was a sobbing mess as I showered and got ready to go to work. I know I can't say anything to my wife about it because the last time I had a bad day, and said something to her about it, she responded with "

Aren't you over that damn dog yet!?!? ".
I can't tell you how you will know when you've really come to terms with your loss, or if you ever really will. I'm beginning to think that it's a sadness that we just learn to live with the rest of our life. I believe in time we learn to enjoy the memories of our past furries, but I'm sure it's bitter-sweet, as we still feel the emptyness too. I remember reading here a while back that a members vet once told her that he still felt a sense of loss over pets that passed many years before.
I too have other fur-kids, and I too fear the day when I'll have to say goodbye. But, I can't imagine my life without them either. I don't feel complete without these little ones around me. So, I'm trying to accept the fact that one day I'll lose another, then another, then another. I don't think it'll be any easier each time than the last, but I'm trying to accept the idea that everything worthwhile has it's price. The price of the unconditional love and comfort from a furry for a dozen or so years is the incredible sadness we feel when we can no longer touch and hold them.
The thing is, I've learned and grown so much from the little lessons my furries have taught me. And the amazing thing is, they're not even trying. They're just doing what's natural for them. I've just learned to pay attention.
Be good to yourself Kimi, it will get better.
Tim