I think my boss will be both relieved and panicked. Relived because we have not been seeing eye-to-eye for a few months now--there were some changes introduced in our company at the end of last year and I strongly disagree with them. It has become clear at this point that I will not be able to fit into this new paradigm, so I think she will be somewhat relieved that I am moving on. At the same time, I think she will be panicked because we are already very short staffed and it will just introduce more stress on her to find my replacement. As for coworkers, I think they'll be pretty surprised, but there is so much turnover here that it won't be a shock.
Emotionally, I waver between extreme excitement and nervousness. I worry about my time off not living up to my expectations and getting depressed. If I have a boring day at work, at least I know that I made money and contributed towards my financial goals, whereas if I have a boring or crappy day when I'm not working, then it seems like it will be a waste. So that puts a lot of pressure on me to really enjoy it! I think it's good that I have over 3 months to prepare myself mentally and hopefully make sure I have plans in place for when I leave so I'm not just sitting around the house.
I know what you mean about trying to get your partner on the same page! I would describe my husband's attitude towards my plans as grudgingly tolerant. We have enough that we would be considered "lean" FIRE'd. Initially the plan was to work for 7-8 more years to get to a FIRE level that would give us a very comfortable retirement, but after a while I started to feel like my life was on hold, and I was just counting down the days, which was not a good feeling. When things went downhill at my current job, I decided to take a "mini-retirement" and then afterwards I could revisit whether to resume full time work or freelance (which would be considerably less remunerative but I think I would enjoy much more). What issues are you facing with your partner?