Sage, I feel for your loss. We had to put Thurman down in February (see avatar) and now two months later, I still encounter every-day things which remind me of him and bring tears to my eyes. You'll probably find over the coming weeks and months the same thing happens to you... and it's okay for that to happen. I've been conditioned over the years not to walk on certain spots on the carpet because that's where Thurman's bed is/was (someone once said the dog trains the human) and even now I still walk around those spots out of habit.
Like Darin said, when a door closes, another opens. I'm sorry for your loss, try to remember the wonderful life you gave him while he was alive. Those memories will help you when those lonely feelings creep in.