It's not really the isolation that gotten to me as I've always loved working in solitude. What's gotten to me during the pandemic, however, is that I don't have access to people when I need it.
That was something that was always part of my life pre-pandemic. I could just call up a friend and go for a coffee post work in the evenings, and that ritual usually indicated that they day was over.
Now with each day being exactly the same as the previous and no intervening activity to extract my mind from work, it's only the weekends that I get to really relax and catch up with things.