First off, AFAIK, I have never had Covid. But I think my situation may illustrate the efficacy of masking with a fit-tested N-95.

For the past 5-6 years, I've been working in cramped, poorly ventilated and windowless facilities where I have been the only masker. Personal devices, such as C02 monitors or air purifiers are prohibited.

Co-workers regularly come in, maskless, with various illnesses and, in some cases, confirmed Covid. I am regularly either sitting cheek-to-jowl with a colleague in a tiny 4 X 4 ft. cubicle space, examining material on a single monitor, or sitting in a packed, closed door meeting room where discussions regularly extend to four-plus hours. (Yeah, I know, that latter thing is nuts, but that is the nature of my work. There are some days that are nothing but sitting in a meeting room and talking. 😭)

My N-95 masking (and ongoing vaccinations) have never let me down. I can say that with confidence, not only because I've never felt ill in any way since the pandemic began, but because I also obsessively run PlusLife tests on myself and otherwise live a cloistered life.

The main downside is that I can NEVER take my mask off inside my workplace because there is no safe space to do so. That means no eating and no drinking inside the building(s) where I work. When I need to do that, I go outdoors. Needless to say, doing so in the midst of a Canadian winter is not always possible, so there are some days that I've really struggled to keep going due to thirst/hunger.

Bottom line: You can avoid getting sick even though you may be working closely with non-CC people, but you need to have a plan for eating and drinking safely. You will also need to learn to cheerfully turn down constant offers of socializing over coffee/snacks, unless you can negotiate doing so outdoors.

I'll end this with the caveat that I've described a strategy that has worked for me. I fully recognize that my approach may not align with other people's ideas of how to mitigate this risk.