Hey sara.b
Firstly: Belated birthday wishes!
Congratulations on another year of experiences and therefore accumulated wisdom.

You might not think to congratulate yourself on this so that is why we others are here.

Secondly, it isn't so much insight, as it is recognition. I have social phobia too, and those are skills I have to practice myself when I go out. I learned them from a social phobia group therapy thing I went to. Sounds kind of odd to do group therapy for social phobia, but it really helped. Some things are more obvious in others, like recognizing patterns and excuses...we are very good at justifying things to ourselves, but really recognize those justifications in others as a defence rather than a reason.

I am so sorry to hear about your dog. I went through that with my two previous dogs, who had to be put down before things got too bad. Trust yourself to know when your pet is not getting any joy in their life, or not getting enough to balance out their pain, or at risk of catastrophic pain.
(By the last category I mean like what was the deciding factor for one of mine: he had bone cancer, which while it was only causing a slight limp, but meant the leg was at risk of breaking easily, which would have put him in great pain, and there would have been no treatment that would help.)
Your pet trusts you, and while it is a huge responsibility, you have built up a relationship that means you deserve that trust, and can make the call at the right time, with the advice of a vet.