The absolutely hardest thing with each of my Basenjis was going through their final week(s) of life.
((hugs)) That's true with all my dogs. I used to say no matter how old, it was still hard. But we lost a 9 mo old Samoyed last December. I'm still crying. No logic.. he didn't know if he lived a long or short life, he just knew he was utterly loved every single day of his life. My heart dog... 6 1/2, lymphoma... had every odds going for her getting a long term remission. She crashed with each protocol and I put her down after 5 mos of her suffering from my desperation to save her. Knowing the end, of course I'd have just kept her comfortable and let her go. Not knowing, I don't know if I would do it different. I hope I would... I hope if it happens again and there isn't a good chance for a cure, I'll let them go. I don't judge anyone who makes a different call, but my heart tells me it was as much my distress at losing her that made me keep on than for her. So I hear you, really clear and with shared pain.
I do hope that you aren't shutting off getting another dog. As terrible as losing them is the emptiness of not having one share your life. It doesn't mend the heart, but it does expand it so the holes left are proportionally smaller.