Do you know that good bye began as "God be with you." It's a good way to part company, much like "Fare well."
When it's time to make an exit, what do you say? The modern way (there are endless Facebook variations) is "it's not about you. It's all about me. This change is good for me and I'm off to pursue my bliss." The focus is on the reasons for leaving. Whatever else is said, whether the rest is in anger or apology, the core message is "I am leaving now because that's what works for me."
And the response to that tends to be "Don't let the door hit you on the way out" (with greater or lesser degrees of courtesy). This is inevitable, since the reasons for leaving are always insufficiency or brokenness or mistakes. When we look at the reasons, we cannot help but feel bad. And there's worse to come.
Human beings are pack animals: we feel abandoned when someone walks away from our pack because we are wired to connect. When someone leaves, they leave a lot of loose ends, connections with nowhere to go.
But human beings are also really, really good at looking forward. Much of the time, that causes us grief because we imagine all the bumps and potholes in the road, all the places we could be ambushed. With some will power, we can push through those visions and see past the obstacles to a destination. We can imagine moving forward and seeing good things on the road ahead.
Every ending reminds us that we are born with an expiry date. They break our favourite things (our habits and assumptions and hopes) and create the restlessness that comes with connections that no longer connect. That's okay. We have the equipment to deal with the hurt and uncertainty and restlessness.
When it's your turn to leave, say "Good bye" and mean it. Don't explain why you are leaving - there is no reason that ties up the loose ends. Instead, say "when I look at your path, I see good things ahead. My wish for you is the strength and resilience to get to the next bright spot on your path."