It's hard to quit anything you've invested time and energy into, especially when it involves relationships with other people. Only way to get better at it, though, is to do it, however hard it is. I awkwardly (and abruptly) quit my first job (for another one) and later ran into my old manager. She brought up how awkward it was, and I replied that I should have done it better. The thing is, I think it was mostly out of shyness, or worry about disappointing someone. But I think that you learn by doing. You get better at framing it correctly, or dealing with objections, and you can quit in a way that brings closure to both parties. People from my past often pop back into it from time to time. It's important to try to leave on good terms whenever possible.