I've said a lot of goodbyes in my life and it never seems to get any easier. I'm lousy at it.
I said goodbye to all my friends when I moved away to start a career and find a new home. I said goodbye to my mother, to better my life. I have to say it every time my parents call. One of the hardest things about it is goodbye usually means you don't get to say hello the next morning. Goodbye calls into question everything you've taken for granted, and all the opportunities you squandered over the time you knew the person.
When you work at such a tight knit place as I do, the word goodbye is all the more difficult. This person I rely on, who I care about, who I see more than my wife, my dog, or my cat just isn't going to be there anymore. And it happens over and over.
It's an odd feeling to think that you now have no obligation to this person. You have no reason to see them other than friendship. You now have to work, and it won't feel as natural, and it won't be as easy. It's not a lot different than moving away from your family, or them moving away from you.
But one of the things that goodbye does present is one of my favorite things: Hello. You get more opportunities to say Hi. Hello will mean more when you say it. It'll mean "I missed you." It'll mean "Finally."
It presents the possibility to say hello to new people and new opportunities. The more you say hello, the more goodbye doesn't seem so bad. You just have to make sure to say hello every chance you get.