When I started my PhD, my supervisor’s wife told me PhD is a lonely path. It’s been quite awhile – I didn’t feel it. It was hard, but I didn’t quite feel it.
Now, I feel it, that loneliness starts to visit – more regularly. But I know, it won’t stay.
In my own case (perhaps not in your case), now I understand – when you don’t feel lonely enough during your PhD time – the universe will sort it out. It will arrange, to make you alone. You totally feel lonely.
That’s the only way, I think, you can finish your PhD.
Do I make sense?