Twice I'd had a 'bad' friday, only to have solutions reveal themselves while I was gardening over the weekend. I realised it did me no harm that my mind strayed to work while gardening, and in fact I was glad of it. So I made a decision to abandon attempts at erecting artificial structure, and quickly realised that trying to impose separations had caused more stress than it resolved.
I found it liberating to stop trying to 'leave work at work', and to not be upset if my thoughts stray to work when I 'should' be off the clock. In return, I stopped trying to block out the rest of my life from my home office. I enjoy a busy life with various community responsibilities and being able to give some attention to these (and family) during 'work hours' is something I value highly. In return I'm happy to perform work activities outside office hours as it suits.
I understand why this won't work for everyone, but for me, trying to set boundaries - which many people had told me was the way to maintain balance - was counter-effective. If anyone is having trouble setting boundaries; consider not.